IS-IS Commands

This module describes the commands used to configure and monitor the Intermediate System-to-Intermediate System (IS-IS) protocol.

For detailed information about IS-IS concepts, configuration tasks, and examples, see the Implementing IS-IS on Cisco IOS XRSoftware module in the Cisco IOS XR Routing Configuration Guide for the Cisco XR 12000 Series Router.

address-family (IS-IS)

To enter address family configuration mode for configuring Intermediate System-to-Intermediate System (IS-IS) routing that use standard IP Version 4 (IPv4) and IP Version 6 (IPv6) address prefixes, use the address-family command in router configuration or interface configuration mode. To disable support for an address family, use the no form of this command.

address-family
{ ipv4 | ipv6 }
{ unicast | mulitcast }

noaddress-family
{ ipv4 | ipv6 }
{ unicast | multicast }

Syntax Description

ipv4

Specifies IPv4 address prefixes.

ipv6

Specifies IPv6 address prefixes.

unicast

Specifies unicast address prefixes.

multicast

Specifies multicast address prefixes.

Command Default

An address family is not specified. The default subaddress family (SAFI) is unicast.

Command Modes

Router configuration

Interface configuration

Command History

Release

Modification

Release 3.2

This command was introduced.

Release 3.4.0

The multicast keyword was added.

Usage Guidelines

Use the address family command to place the router or interface in address family configuration mode. In router address family configuration mode, you can configure routing that uses standard IPv4 or IPv6 address prefixes. An address family must be specified in interface configuration mode. In interface address family configuration mode, you can alter interface parameters for IPv4or IPv6.

You must specify an address family in order to configure parameters that pertain to a single address family.

Task ID

Task ID

Operations

isis

read, write

Examples

The following example shows how to configure the IS-IS router process with IPv4 unicast address prefixes:

address-family multicast topology (IS-IS)

To enable a multicast topology when configuring Intermediate System-to-Intermediate System (IS-IS) routing (or to place a given topology within the IS-IS interface), use the address-family multicast topology command with either IPv4 or IPv6 address prefix in the appropriate configuration mode. To disable a multicast topology in IS-IS, use the no form of this command.

Command Default

An address family for multicast topology is not specified. The default subaddress family (SAFI) is unicast.

Command Modes

Router configuration

Interface configuration

Command History

Release

Modification

Release 3.7.0

This command was introduced.

Usage Guidelines

Use the address family multicast topology command to place the router or interface in address family configuration mode. In router address family configuration mode, you can associate an IS-IS topology ID with the topology you have created to add connected and local routes to a specific routing table.

Task ID

Task ID

Operations

isis

read, write

Examples

The following example shows how to configure the IS-IS router topology with an IPv4 multicast address prefix:

Related Commands

Associates a topology ID with a named IS-IS topology to differentiate topologies in the domain.

adjacency-check disable

To suppress Intermediate System-to-Intermediate System (IS-IS) IP Version 4 (IPv4) or IP Version 6 (IPv6) protocol-support consistency checks that are performed prior to forming adjacencies on hello packets, use the adjacency-check disable command in address family configuration mode. To remove this function, use the no form of this command.

adjacency-checkdisable

noadjacency-checkdisable

Command Default

Adjacency check is enabled

Command Modes

Address family configuration

Command History

Release

Modification

Release 3.2

This command was introduced.

Usage Guidelines

IS-IS performs consistency checks on hello packets and forms an adjacency only with a neighboring router that supports the same set of protocols. A router running IS-IS for both IPv4 and IPv6 does not form an adjacency with a router running IS-IS for IPv4 only.

Use the adjacency-check disable command to suppress the consistency checks for IPv6 IS-IS and allow an IPv4 IS-IS router to form an adjacency with a router running IPv4 IS-IS and IPv6. IS-IS never forms an adjacency between a router running IPv4 IS-IS only and a router running IPv6 only.

In addition, the adjacency-check disable command suppresses the IPv4 or IPv6 subnet consistency check and allows IS-IS to form an adjacency with other routers regardless of whether they have an IPv4 or IPv6 subnet in common.

Task ID

Task ID

Operations

isis

read, write

Examples

The command in the following example disables the adjacency checks:

The following example shows how the network administrator introduces IPv6 into an existing IPv4 IS-IS network and ensures that the checking of hello packet checks from adjacent neighbors is disabled until all neighbor routers are configured to use IPv6:

attached-bit receive ignore

To ignore the attached bit in a received Level 1 link-state packet (LSP), use the attached-bit receive ignore command in address family configuration mode. To remove the attached-bit receive ignore command from the configuration file and restore the system to its default condition, use the no form of this command.

attached-bitreceiveignore

noattached-bitreceiveignore

Command Default

The attached bit is set in the LSP.

Command Modes

Address family configuration

Command History

Release

Modification

Release 3.8.0

This command was introduced.

Usage Guidelines

Task ID

Task ID

Operations

isis

read, write

Examples

The following example shows how to configure to ignore the attached bit in a received LSP:

Related Commands

Configures an Intermediate System-to-Intermediate System (IS-IS) instance with an attached bit in the Level 1 link-state packet (LSP).

attached-bit send

To configure an Intermediate System-to-Intermediate System (IS-IS) instance with an attached bit in the Level 1 link-state packet (LSP), use the attached-bit send command in address family configuration mode. To remove the attached-bit sendcommand from the configuration file and restore the system to its default condition, use the no form of this command.

attached-bitsend
{ always-set | never-set }

noattached-bitsend
{ always-set | never-set }

Syntax Description

always-set

Specifies to always set the attached bit in the LSP.

never-set

Specifies to never set the attached bit in the LSP.

Command Default

The attached bit is not forced to be set or unset in the LSP.

Command Modes

Address family configuration

Command History

Usage Guidelines

Use the attached-bit send command to set an IS-IS instance with an attached bit in the Level 1 LSP that allows another IS-IS instance to redistribute Level 2 topology. The attached bit is used when the Level 2 connectivity from another IS-IS instance is advertised by the Level 1 attached bit.

Cisco IOS XR software does not support multiple Level 1 areas in a single IS-IS routing instance; however the equivalent functionality is achieved by redistribution of routes between two IS-IS instances by using the redistribute (IS-IS) command.

The attached bit is configured for a specific address family only if the single-topology command is not configured.

Note

If connectivity for the Level 2 instance is lost, the attached bit in the Level 1 instance LSP continues sending traffic to the Level 2 instance and causes the traffic to be dropped.

Task ID

Task ID

Operations

isis

read, write

Examples

The following example shows how to configure an Intermediate System-to-Intermediate System (IS-IS) instance with an attached bit:

circuit-type

To configure the type of adjacency used for the Intermediate System-to-Intermediate System (IS-IS) protocol, use the circuit-type command in interface configuration mode. To reset the circuit type to Level l and Level 2, use the no form of this command.

circuit-type
{ level-1 | level-1-2 | level-2-only }

nocircuit-type

Syntax Description

level-1

Establishes only Level 1 adjacencies over an interface.

level-1-2

Establishes both Level 1 and Level 2 adjacencies, if possible.

level-2-only

Establishes only Level 2 adjacencies over an interface.

Command Default

Default adjacency types are Level 1 and Level 2 adjacencies.

Command Modes

Interface configuration

Command History

Release

Modification

Release 3.2

This command was introduced.

Usage Guidelines

Adjacencies may not be established even if allowed by the circuit-type command. The proper way to establish adjacencies is to configure a router as a Level 1, Level 1 and Level 2, or Level 2-only system using the is-typecommand. Only on networking devices that are between areas (Level 1 and Level 2 networking devices) should you configure some interfaces to be Level 2-only to prevent wasting bandwidth by sending out unused Level 1 hello packets. Remember that on point-to-point interfaces, the Level 1 and Level 2 hello packets are in the same packet.

Task ID

Task ID

Operations

isis

read, write

Examples

The following example shows how to configure a Level 1 adjacency with its neighbor on GigabitEthernetinterface 0/2/0/0 and Level 2 adjacencies with all Level 2-capable routers on GigabitEthernet interface 0/5/0/2:

Related Commands

clear isis process

To clear the link-state packet (LSP) database and adjacency database sessions for an Intermediate System-to-Intermediate System (IS-IS) instance or all IS-IS instances, use the clear isis process command in EXEC configuration mode.

Related Commands

csnp-interval

To configure the interval at which periodic complete sequence number PDU (CSNP) packets are sent on broadcast interfaces, use the csnp-interval command in interface configuration mode. To restore the default value, use the noform of this command.

csnp-intervalseconds
[ level
{ 1 | 2 } ]

no csnp-intervalseconds
[ level
{ 1 | 2 } ]

Syntax Description

seconds

Interval (in seconds) of time between transmission of CSNPs on multiaccess networks. This interval applies only for the designated router. Range is 0 to 65535 seconds.

level {1 | 2}

(Optional) Specifies the interval of time between transmission of CSNPs for Level 1 or Level 2 independently.

Command Default

seconds: 10 seconds

Both Level 1 and Level 2 are configured if no level is specified.

Command Modes

Interface configuration

Command History

Release

Modification

Release 2.0

This command was introduced.

Command History

Release

Modification

Release 3.2

This command was introduced.

Usage Guidelines

The csnp-interval command applies only to the designated router (DR) for a specified interface. Only DRs send CSNP packets to maintain database synchronization. The CSNP interval can be configured independently for Level 1 and Level 2.

Use of the csnp-interval command on point-to-point subinterfaces makes sense only in combination with the IS-IS mesh-group feature.

Task ID

Task ID

Operations

isis

execute

rib

read, write

basic-services

read, write

Examples

The following example shows how to set the CSNP interval for Level 1 to 30 seconds:

default-information originate (IS-IS)

To generate a default route into an Intermediate System-to-Intermediate System (IS-IS) routing domain, use the default-information originate command in address family configuration mode. To remove the default-information originate command from the configuration file and restore the system to its default condition, use the no form of this command.

Command Default

Command Modes

Command History

The route-mapmap-name keyword and argument were changed to route-policy route-policy-name.

Usage Guidelines

If a router configured with the default-information originate command has a route to 0.0.0.0 in the routing table, IS-IS originates an advertisement for 0.0.0.0 in its link-state packets (LSPs).

Without a route policy, the default is advertised only in Level 2 LSPs. For Level 1 routing, there is another process to find the default route, which is to look for the closest Level 1 and Level 2 router. The closest Level 1 and Level 2 router can be found by looking at the attached-bit (ATT) in Level 1 LSPs.

A route policy can be used for two purposes:

To make the router generate the default route in its Level 1 LSPs.

To advertise 0.0.0.0/0 conditionally.

Task ID

Task ID

Operations

isis

read, write

Examples

The following example shows how to generate a default external route into an IS-IS domain:

Related Commands

disable (IS-IS)

To disable the Intermediate System-to-Intermediate System (IS-IS) topology on a specified interface, use the disable command in interface address family configuration mode. To remove this function, use the no form of this command.

disable

nodisable

Command Default

IS-IS protocol is enabled.

Command Modes

Interface address family configuration

Command History

Release

Modification

Release 3.2

This command was introduced.

Usage Guidelines

Task ID

Task ID

Operations

isis

read, write

Examples

The following example shows how to disable the IS-IS protocol for IPv4 unicast on GigabitEthernet interface 0/1/0/1:

distance (IS-IS)

To define the administrative distance assigned to routes discovered by the Intermediate System-to-Intermediate System (IS-IS) protocol, use the distance command in address family configuration mode. To remove the distance command from the configuration file and restore the system to its default condition in which the software removes a distance definition, use the no form of this command.

(Optional) The length of the IP prefix. A decimal value that indicates how many of the high-order contiguous bits of the address compose the prefix (the network portion of the address). A slash must precede the decimal value. Range is 0 to 32 for IPv4 addresses and 0 to 128 for IPv6 addresses.

prefix-list-name

(Optional) List of routes to which administrative distance applies.

Command Default

weight: 115

Command Modes

Address family configuration

Command History

Release

Modification

Release 3.2

This command was introduced.

Usage Guidelines

An administrative distance is an integer from 1 to 255. In general, the higher the value, the lower the trust rating. An administrative distance of 255 means that the routing information source cannot be trusted at all and should be ignored. Weight values are subjective; no quantitative method exists for choosing weight values.

Use the distance command to configure the administrative distances applied to IS-IS routes when they are inserted into the Routing Information Base (RIB), and influence the likelihood of these routes being preferred over routes to the same destination addresses discovered by other protocols.

The address/prefix-length argument defines to which source router the distance applies. In other words, each IS-IS route is advertised by another router, and that router advertises an address that identifies it. This source address is displayed in the output of the show isis route detail command.

The distance command applies to the routes advertised by routers whose address matches the specified prefix. The prefix-list-name argument can then be used to refine this further so that the distance command affects only specific routes.

Task ID

Task ID

Operations

isis

read, write

Examples

In the following example, a distance of 10 is assigned to all routes to 2.0.0.0/8 and 3.0.0.0/8 (or more specific prefixes) that are advertised by routers whose ID is contained in 1.0.0.0/8. A distance of 80 is assigned to all other routes.

fast-reroute per-link (IS-IS)

To enable IP fast reroute (IPFRR) loop-free alternate (LFA) prefix independent per-link computation, use the fast-reroute per-link command in interface address family configuration mode. To disable this feature, use the no form of this command.

Specifies an interface that needs to be either excluded from FRR LFA computation (when used with exclude keyword) or to be included to LFA candidate list in FRR LFA computation (when used with the lfa-candidate keyword).

type

Interface type. For more information, use the question mark ( ? ) online help function.

interface-path-id

Physical interface or virtual interface.

Note

Use the show interfaces command to see a list of all interfaces currently configured on the router.

For more information about the syntax for the router, use the question mark ( ? ) online help function.

Command Default

IP fast-reroute LFA per-link computation is disabled.

Command Modes

Interface address family configuration

Command History

Release

Modification

Release 4.0.1

This command was introduced.

Usage Guidelines

Task ID

Task ID

Operation

isis

read, write

Examples

This example shows how to configure per-link fast-reroute LFA computation for the IPv4 unicast topology at Level 1:

Related Commands

fast-reroute per-prefix (IS-IS)

To enable IP fast reroute (IPFRR) loop-free alternate (LFA) prefix dependent computation, use the fast-reroute per-prefix command in interface address family configuration mode. LFA is supported only on Enhanced Ethernet line card. To disable this feature, use the no form of this command.

Specifies an interface that needs to be either excluded from FRR LFA computation (when used with exclude keyword) or to be included to LFA candidate list in FRR LFA computation (when used with the lfa-candidate keyword).

type

Interface type. For more information, use the question mark ( ? ) online help function.

interface-path-id

Physical interface or virtual interface.

Note

Use the show interfaces command to see a list of all interfaces currently configured on the router.

For more information about the syntax for the router, use the question mark ( ? ) online help function.

Command Default

IP fast-reroute LFA per-prefix computation is disabled.

Command Modes

Interface address family configuration

Command History

Release

Modification

Release 4.0.1

This command was introduced.

Usage Guidelines

Task ID

Task ID

Operation

isis

read, write

Examples

This example shows how to configure per-prefix fast-reroute LFA computation for the IPv4 unicast topology at Level 1:

Related Commands

fast-reroute per-link priority-limit (IS-IS)

To enable the IP fast reroute (IPFRR) loop-free alternate (LFA) prefix independent per-link computation, use the fast-reroute per-link priority-limit command in address family configuration mode. To disable this feature, use the no form of this command.

fast-reroute per-prefix load-sharing disable (IS-IS)

To disable load sharing prefixes across multiple backups, use the fast-reroute per-prefix load-sharing disable command in IPv4 address family configuration mode. To disable this feature, use the no form of this command.

fast-rerouteper-prefixload-sharingdisable

nofast-rerouteper-prefixload-sharingdisable

Syntax Description

level {1|2}

Disables load-sharing for Level 1 or Level 2 independently.

Command Default

Load sharing is enabled.

Command Modes

IPv4 unicast address family configuration

IPv4 multicast address family configuration

Command History

Release

Modification

Release 4.0.1

This command was introduced.

Usage Guidelines

Task ID

Task ID

Operations

isis

read, write

Examples

This example shows how to disable load-sharing prefixes across multiple backups for level 1 routes:

fast-reroute per-prefix tiebreaker (IS-IS)

To configure tie-breaker for multiple backups, use the fast-reroute per-prefix tiebreaker command in IPv4 address family configuration mode. To disable tie-breaker configuration, use the no form of this command.

hello-interval (IS-IS)

To specify the length of time between consecutive hello packets sent by the Intermediate System-to-Intermediate System (IS-IS) protocol software, use the hello-interval command in interface configuration mode. To restore the default value, use the no form of this command.

hello-intervalseconds
[ level
{ 1 | 2 } ]

nohello-interval [seconds]
[ level
{ 1 | 2 } ]

Syntax Description

seconds

Integer value (in seconds) for the length of time between consecutive hello packets. By default, a value three times the hello interval seconds is advertised as the hold time in the hello packets sent. (That multiplier of three can be changed by using the hello-multiplier command.) With smaller hello intervals, topological changes are detected more quickly, but there is more routing traffic. Range is 1 to 65535 seconds.

Command Default

Command Modes

Interface configuration

Command History

Release

Modification

Release 3.2

This command was introduced.

Usage Guidelines

The hello interval can be configured independently for Level 1 and Level 2, except on serial point-to-point interfaces. (Because only a single type of hello packet is sent on serial links, it is independent of Level 1 or Level 2.) Configuring Level 1 and Level 2 independently is used on LAN interfaces.

Note

A shorter hello interval gives quicker convergence, but increases bandwidth and CPU usage. It might also add to instability in the network.

A slower hello interval saves bandwidth and CPU. Especially when used in combination with a higher hello multiplier, this strategy may increase overall network stability.

For point-to-point links, IS-IS sends only a single hello for Level 1 and Level 2, making the level keyword meaningless on point-to-point links. To modify hello parameters for a point-to-point interface, omit the level keyword.

Task ID

Task ID

Operations

isis

read, write

Examples

The following example shows how to configure TenGigE interface 0/6/0/0 to advertise hello packets every 5 seconds for Level 1 topology routes. This situation causes more traffic than configuring a longer interval, but topological changes are detected more quickly.

Related Commands

Specifies the number of IS-IS hello packets a neighbor must miss before the router should declare the adjacency as down.

hello-multiplier

To specify the number of Intermediate System-to-Intermediate System (IS-IS) hello packets a neighbor must miss before the router should declare the adjacency as down, use the hello-multiplier command in interface configuration mode. To restore the default value, use the no form of this command.

hello-multipliermultiplier
[ level
{ 1 | 2 } ]

nohello-multiplier [multiplier]
[ level
{ 1 | 2 } ]

Syntax Description

multiplier

Advertised hold time in IS-IS hello packets is set to the hello multiplier times the hello interval. Range is 3 to 1000. Neighbors declare an adjacency to this down router after not having received any IS-IS hello packets during the advertised hold time. The hold time (and thus the hello multiplier and the hello interval) can be set on an individual interface basis, and can be different between different networking devices in one area.

Using a smaller hello multiplier gives faster convergence, but can result in more routing instability. Increase the hello multiplier to a larger value to help network stability when needed. Never configure a hello multiplier to a value lower than the default value of 3.

Command Default

Command Modes

Interface configuration

Command History

Release

Modification

Release 3.2

This command was introduced.

Usage Guidelines

The “holding time” carried in an IS-IS hello packet determines how long a neighbor waits for another hello packet before declaring the neighbor to be down. This time determines how quickly a failed link or neighbor is detected so that routes can be recalculated.

Use the hello-multiplier command in circumstances where hello packets are lost frequently and IS-IS adjacencies are failing unnecessarily. You can raise the hello multiplier and lower the hello interval (hello-interval (IS-IS)command) correspondingly to make the hello protocol more reliable without increasing the time required to detect a link failure.

On point-to-point links, there is only one hello for both Level 1 and Level 2. Separate Level 1 and Level 2 hello packets are also sent over nonbroadcast multiaccess (NBMA) networks in multipoint mode, such as X.25, Frame Relay, and ATM.

Task ID

Task ID

Operations

isis

read, write

Examples

The following example shows how the network administrator wants to increase network stability by making sure an adjacency goes down only when many (ten) hello packets are missed. The total time to detect link failure is 60 seconds. This strategy ensures that the network remains stable, even when the link is fully congested.

Related Commands

Specifies the length of time between hello packets that the software sends.

hello-padding

To configure padding on Intermediate System-to-Intermediate System (IS-IS) hello protocol data units (IIH PDUs) for all IS-IS interfaces on the router, use the hello-padding command in interface configuration mode. To suppress padding, use the no form of this command.

Syntax Description

Command Default

Hello padding is enabled.

Command Modes

Interface configuration

Command History

Release

Modification

Release 3.2

This command was introduced.

Usage Guidelines

You might want to suppress hello padding to conserve network resources. The lower the circuit speed, the higher the percentage of padding overhead. Before suppressing the hello padding, you should know your physical and data link layer configurations and have control over them, and also know your router configuration at the network layer.

For point-to-point links, IS-IS sends only a single hello for Level 1 and Level 2, making the level keyword meaningless on point-to-point links. To modify hello parameters for a point-to-point interface, omit the level keyword.

Task ID

Task ID

Operations

isis

read, write

Examples

The following example shows how to suppress IS-IS hello padding over local area network (LAN) circuits for interface GigabitEthernet 0/2/0/1:

Related Commands

hello-password

To configure the authentication password for an Intermediate System-to-Intermediate System (IS-IS) interface, use the hello-password command in interface configuration mode. To disable authentication, use the no form of this command.

Syntax Description

(Optional) Specifies that the password use clear text password authentication.

clear

(Optional) Specifies that the password be unencrypted.

encrypted

(Optional) Specifies that the password be encrypted using a two-way algorithm.

password

Authentication password you assign for an interface.

level {1 | 2}

(Optional) Specifies whether the password is for a Level 1 or a Level 2 protocol data unit (PDU).

send-only

(Optional) Specifies that the password applies only to protocol data units (PDUs) that are being sent and does not apply to PDUs that are being received.

Command Default

Both Level 1 and Level 2 are configured if no level is specified.

password: encrypted text

Command Modes

Interface configuration

Command History

Release

Modification

Release 3.2

This command was introduced.

Release 3.5.0

The keychainkeychain-name keyword and argument were added.

Release 3.7.0

Removed the keychain keyword and added the hello-password keychain command as a separate command from the hello-password command. Updated the syntax of the hello-password command.

Usage Guidelines

When a text password is configured, it is exchanged as clear text. Therefore, the hello-password command provides limited security.

When an hmac-md5 password is configured, the password is never sent over the network and is instead used to calculate a cryptographic checksum to ensure the integrity of the exchanged data.

For point-to-point links, IS-IS sends only a single hello for Level 1 and Level 2, making the level keyword meaningless on point-to-point links. To modify hello parameters for a point-to-point interface, omit the level keyword.

Task ID

Task ID

Operations

isis

read, write

Examples

The following example shows how to configure a password with HMAC-MD5 authentication for hello packets running on GigabitEthernet 0/2/0/3 interface:

Related Commands

Configures an additional authentication password for an IS-IS interface.

hello-password keychain

To configure the authentication password keychain for an Intermediate System-to-Intermediate System (IS-IS) interface, use the hello-password keychain command in interface configuration mode. To disable the authentication password keychain, use the no form of this command.

hello-passwordkeychainkeychain-name
[ level
{ 1 | 2 } ]
[send-only]

nohello-passwordkeychainkeychain-name
[ level
{ 1 | 2 } ]
[send-only]

Syntax Description

keychain

Keyword that specifies the keychain to be configured. An authentication password keychain is a sequence of keys that are collectively managed and used for authenticating a peer-to-peer group.

keychain-name

Specifies the name of the keychain.

level {1 | 2}

(Optional) Specifies whether the keychain is for a Level 1 or a Level 2 protocol data unit (PDU).

send-only

(Optional) Specifies that the keychain applies only to protocol data units (PDUs) that are being sent and does not apply to PDUs that are being received.

Command Default

Both Level 1 and Level 2 are configured if no level is specified.

password: encrypted text

Command Modes

Interface configuration

Command History

Release

Modification

Release 3.2

This command was introduced.

Release 3.5.0

The keychainkeychain-name keyword and argument were added.

Release 3.7.0

Separated the hello-password keychain command as a separate command from the hello-password command, and updated the syntax of the hello-password command.

Usage Guidelines

Specify a keychain to enable keychain authentication between two IS-IS peers. Use the keychainkeychain-name keyword and argument to implement hitless key rollover for authentication.

Task ID

Task ID

Operations

isis

read, write

Examples

The following example shows how to configure a password keychain for level 1, send only authentication on a GigabitEthernet interface:

Related Commands

Configures an additional authentication password for an IS-IS interface.

hello-password accept

To configure an additional authentication password for an Intermediate System-to-Intermediate System (IS-IS) interface, use the hello-password accept command in interface configuration mode. To disable authentication, use the no form of this command.

Command Default

Both Level 1 and Level 2 are configured if no level is specified.

Command Modes

Interface configuration

Command History

Release

Modification

Release 3.2

This command was introduced.

Usage Guidelines

Use the hello-password accept command to add an additional password for an IS-IS interface. An authentication password must be configured using the hello-password command before an accept password can be configured for the corresponding level.

Related Commands

hostname dynamic disable

To disable Intermediate System-to-Intermediate System (IS-IS) routing protocol dynamic hostname mapping, use the hostname dynamic command in router configuration mode. To remove the specified command from the configuration file and restore the system to its default condition, use the no form of this command.

hostnamedynamicdisable

nohostnamedynamicdisable

Syntax Description

disable

Disables dynamic host naming.

Command Default

Router names are dynamically mapped to system IDs.

Command Modes

Router configuration

Command History

Release

Modification

Release 3.2

This command was introduced.

Usage Guidelines

In an IS-IS routing domain, each router is represented by a 6-byte hexadecimal system ID. When network administrators maintain and troubleshoot networking devices, they must know the router name and corresponding system ID.

Link-state packets (LSPs) include the dynamic hostname in the type, length, and value (TLV) which carries the mapping information across the entire domain. Every router in the network, upon receiving the TLV from an LSP, tries to install it in a mapping table. The router then uses the mapping table when it wants to convert a system ID to a router name.

To display the entries in the mapping tables, use the show isis hostname command.

Task ID

Task ID

Operations

isis

read, write

Examples

The following example shows how to disable dynamic mapping of hostnames to system IDs:

Related Commands

ignore-lsp-errors

To override the default setting of a router to ignore Intermediate System-to-Intermediate System (IS-IS) link-state packets (LSPs) that are received with internal checksum errors, use the ignore-lsp-errorsdisable command in router configuration mode. To enable ignoring IS-IS LSP errors, use the no form of this command.

ignore-lsp-errorsdisable

noignore-lsp-errorsdisable

Syntax Description

disable

Disables the functionality of the command.

Command Default

The system purges corrupt LSPs that cause the initiator to regenerate LSPs.

Command Modes

Router configuration

Command History

Release

Modification

Release 3.2

This command was introduced.

Usage Guidelines

The IS-IS protocol definition requires that a received LSP with an incorrect data-link checksum be purged by the receiver, which causes the initiator of the packet to regenerate it. However, if a network has a link that causes data corruption and at the same time is delivering LSPs with correct data-link checksums, a continuous cycle of purging and regenerating large numbers of packets can occur. Because this situation could render the network nonfunctional, use this command to ignore these LSPs rather than purge the packets.

The receiving network devices use link-state packets to maintain their routing tables.

Task ID

Task ID

Operations

isis

read, write

Examples

The following example shows how to instruct the router to ignore LSPs that have internal checksum errors:

interface (IS-IS)

To configure the Intermediate System-to-Intermediate System (IS-IS) protocol on an interface, use the interface command in router configuration mode. To disable IS-IS routing for interfaces, use the noform of this command.

interfacetypeinterface-path-id

nointerfacetypeinterface-path-id

Syntax Description

type

Interface type. For more information, use the question mark (?) online help function.

interface-path-id

Physical interface or virtual interface.

Note

Use the showinterfaces command to see a list of all interfaces currently configured on the router.

For more information about the syntax for the router, use the question mark (?) online help function.

Command Default

No interfaces are specified.

Command Modes

Router configuration

Command History

Release

Modification

Release 3.2

This command was introduced.

Usage Guidelines

An address family must be established on the IS-IS interface before the interface is enabled for IS-IS protocol operation.

Task ID

Task ID

Operations

isis

read, write

Examples

The following example shows how to enable an IS-IS multitopology configuration for IPv4 on GigabitEthernet interface 0/3/0/0:

ispf

To configure the incremental shortest path first (iSPF) algorithm to calculate network topology, use the ispf command in address family configuration mode. To disable this algorithm function, use the no form of this command.

is-type

To configure the routing level for an Intermediate System-to-Intermediate System (IS-IS) area, use the is-type command in router configuration mode. To set the routing level to the default level, use the noform of this command.

is-type
{ level-1 | level-1-2 | level-2-only }

nois-type
[ level-1 | level-1-2 | level-2-only ]

Syntax Description

level-1

Specifies that the router perform only Level 1 (intra-area) routing. This router learns only about destinations inside its area. Level 2 (interarea) routing is performed by the closest Level 1-2 router.

level-1-2

Specifies that the router perform both Level 1 and Level 2 routing.

level-2-only

Specifies that the routing process acts as a Level 2 (interarea) router only. This router is part of the backbone, and does not communicate with Level 1-only routers in its own area.

Command Default

Both Level 1 and Level 2 are configured if no level is specified.

Command Modes

Router configuration

Command History

Release

Modification

Release 3.2

This command was introduced.

Usage Guidelines

When the router is configured with Level 1 routing only, this router learns about destinations only inside its area. Level 2 (interarea) routing is performed by the closest Level 1-2 router.

When the router is configured with Level 2 routing only, this router is part of the backbone, and does not communicate with Level 1 routers in its own area.

The router has one link-state packet database (LSDB) for destinations inside the area (Level 1 routing) and runs a shortest path first (SPF) calculation to discover the area topology. It also has another LSDB with link-state packets (LSPs) of all other backbone (Level 2) routers, and runs another SPF calculation to discover the topology of the backbone and the existence of all other areas.

We highly recommend that you configure the type of an IS-IS routing process to establish the proper level of adjacencies. If there is only one area in the network, there is no need to run both Level 1 and Level 2 routing algorithms.

Task ID

Task ID

Operations

isis

read, write

Examples

The following example shows how to specify that the router is part of the backbone and that it does not communicate with Level 1-only routers:

Related Commands

log adjacency changes (IS-IS)

To cause an IS-IS instance to generate a log message when an Intermediate System-to-Intermediate System (IS-IS) adjacency changes state (up or down), use the log adjacency changes command in router configuration mode. To restore the default value, use the no form of this command.

logadjacencychanges

nologadjacencychanges

Command Default

No IS-IS instance log messages are generated.

Command Modes

Router configuration

Command History

Release

Modification

Release 3.2

This command was introduced.

Usage Guidelines

Use the log adjacency changes command to monitor IS-IS adjacency state changes; it may be very useful when you are monitoring large networks. Messages are logged using the system error message facility. Messages can be in either of two forms:

Examples

Related Commands

Command

Description

logging

Logs messages to a syslog server host.

log pdu drops

To log Intermediate System-to-Intermediate System (IS-IS) protocol data units (PDUs) that are dropped, use the log pdu drops command in router configuration mode. To disable this function, use the no form of this command.

logpdudrops

nologpdudrops

Command Default

PDU logging is disabled.

Command Modes

Router configuration

Command History

Release

Modification

Release 3.2

This command was introduced.

Usage Guidelines

Use the log pdu drops command to monitor a network when IS-IS PDUs are suspected of being dropped. The reason for the PDU being dropped and current PDU drop statistics are recorded.

Syntax Description

Command Default

10 LSPs are allowed in a back-to-back window

Command Modes

Interface configuration

Command History

Release

Modification

Release 3.4.0

This command was introduced.

Usage Guidelines

Use the lsp fast-flood threshold command to accelerate convergence of LSP database. LSPs are sent back-to-back over an interface up to the specified limit. Past the limit, LSPs are sent out in the next batch window as determined by LSP pacing interval.

Syntax Description

Specifies the hold time between the first and second LSP generation (in milliseconds). Range is 1 to 120000 milliseconds.

maximum-wait maximum

Specifies the maximum interval (in milliseconds) between two consecutive occurrences of an LSP being generated. Range is 1 to 120000 milliseconds.

level {1 | 2}

(Optional) Specifies the LSP time interval for Level 1 or Level 2 independently.

Command Default

initial-wait initial: 50 milliseconds

secondary-wait secondary: 200 milliseconds

maximum-wait maximum: 5000 milliseconds

Command Modes

Router configuration

Command History

Release

Modification

Release 3.2

This command was introduced.

Usage Guidelines

During prolonged periods of network instability, repeated recalculation of LSPs can cause increased CPU load on the local router. Further, the flooding of these recalculated LSPs to the other Intermediate Systems in the network causes increased traffic and can result in other routers having to spend more time running route calculations.

Use the lsp-gen-interval command to reduce the rate of LSP generation during periods of instability in the network. This command can help to reduce CPU load on the router and to reduce the number of LSP transmissions to its IS-IS neighbors.

Task ID

Task ID

Operations

isis

read, write

Examples

The following example shows how to set the maximum interval between two consecutive occurrences of an LSP to 15 milliseconds and the initial LSP generation delta to 5 milliseconds:

Related Commands

Configures the amount of time between retransmission of each IS-IS LSP on a point-to-point link.

lsp-interval

To configure the amount of time between consecutive link-state packets (LSPs) sent on an Intermediate System-to-Intermediate System (IS-IS) interface, use the lsp-interval command in interface configuration mode. To restore the default value, use the no form of this command.

lsp-intervalmilliseconds
[ level
{ 1 | 2 } ]

nolsp-interval [milliseconds]
[ level
{ 1 | 2 } ]

Syntax Description

milliseconds

Time delay (in milliseconds) between successive LSPs. Range is 1 to 4294967295.

level {1 | 2}

(Optional) Configures the LSP time delay for Level 1 or Level 2 independently.

Command Default

milliseconds: 33 milliseconds

Command Modes

Interface configuration

Command History

Release

Modification

Release 3.2

This command was introduced.

Usage Guidelines

Task ID

Task ID

Operations

isis

read, write

Examples

The following example shows how to cause the system to send LSPs every 100 milliseconds (10 packets per second) on Level 1 and Level 2:

Related Commands

Configures the amount of time between retransmission of each IS-IS LSP on a point-to-point link.

lsp-mtu

To set the maximum transmission unit (MTU) size of Intermediate System-to-Intermediate System (IS-IS) link-state packets (LSPs), use the lsp-mtucommand in router configuration mode. To restore the default, use the no form of this command.

lsp-mtubytes
[ level
{ 1 | 2 } ]

nolsp-mtu [bytes]
[ level
{ 1 | 2 } ]

Syntax Description

bytes

Maximum packet size in bytes. The number of bytes must be less than or equal to the smallest MTU of any link in the network. Range is 128 to 4352 bytes.

level {1 | 2}

(Optional) Specifies routing Level 1 or Level 2 independently.

Command Default

Both Level 1 and Level 2 are configured if no level is specified.

Command Modes

Router configuration

Command History

Release

Modification

Release 3.2

This command was introduced.

Usage Guidelines

Under normal conditions, the default MTU size should be sufficient. However, if the MTU size of a link is less than 1500 bytes, the LSP MTU size must be lowered accordingly on each router in the network. If this action is not taken, routing becomes unpredictable.

This guideline applies to all Cisco networking devices in a network. If any link in the network has a reduced MTU size, all devices must be changed, not just the devices directly connected to the link.

Note

Do not set the lsp-mtu command (network layer) to a value greater than the link MTU size that is set with the mtu command (physical layer).

Related Commands

lsp-password

To configure the link-state packet (LSP) authentication password, use the lsp-password command in router configuration mode. To remove the lsp-password command from the configuration file and disable link-state packet authentication, use the noform of this command.

(Optional) Adds passwords to LSP and sequence number protocol (SNP) data units when they are sent. Does not check for authentication in received LSPs or sequence number PDUs (SNPs).

snp send-only

(Optional) Adds passwords to SNP data units when they are sent. Does not check for authentication in received SNPs. This option is available when the text keyword is specified.

Command Default

Both Level 1 and Level 2 are configured if no level is specified.

Command Modes

Router configuration

Command History

Release

Modification

Release 3.2

This command was introduced.

Release 3.5.0

The keychainkeychain-name keyword and argument were added.

Usage Guidelines

When a text password is configured, it is exchanged as clear text. Therefore, the lsp-password command provides limited security.

When an HMAC-MD5 password is configured, the password is never sent over the network and is instead used to calculate a cryptographic checksum to ensure the integrity of the exchanged data.

The recommended password configuration is that both incoming and outgoing SNPs be authenticated.

Note

To disable SNP password checking, the snp send-only keywords must be specified in the lsp-password command.

To configure an additional password, use the lsp-password accept command.

Specify a key chain to enable key chain authentication between two IS-IS peers. Use the keychainkeychain-name keyword and argument to implement hitless key rollover for authentication.

Task ID

Task ID

Operations

isis

read, write

Examples

The following example shows how to configure separate Level 1 and Level 2 LSP and SNP passwords, one with HMAC-MD5 authentication and encryption and one with clear text password authentication and no encryption:

Related Commands

Configures an additional LSP password when one LSP password is already configured for a level.

lsp-password accept

To configure an additional link-state packet (LSP) authentication password, use the lsp-password accept command in router configuration mode. To remove the lsp-password accept command from the configuration file and restore the system to its default condition, use the noform of this command.

Command Default

Both Level 1 and Level 2 are configured if no level is specified.

Command Modes

Router configuration

Command History

Release

Modification

Release 3.2

This command was introduced.

Usage Guidelines

The lsp-password accept command adds an additional password for use when the system validates incoming LSPs and sequence number PDUs (SNPs). An LSP password must be configured using the lsp-password command before an accept password can be configured for the corresponding level.

Task ID

Task ID

Operations

isis

read, write

Examples

The following example shows how to configure an accept Level 1 LSP and SNP password:

Related Commands

lsp-refresh-interval

To set the time between regeneration of link-state packets (LSPs) that contain different sequence numbers, use the lsp-refresh-interval command in router configuration mode. To restore the default refresh interval, use the no form of this command.

lsp-refresh-intervalseconds
[ level
{ 1 | 2 } ]

nolsp-refresh-interval
[ seconds
[ level
{ 1 | 2 } ] ]

Syntax Description

seconds

Refresh interval (in seconds). Range is 1 to 65535 seconds.

level {1 | 2}

(Optional) Specifies routing Level 1 or Level 2 independently.

Command Default

seconds: 900 seconds (15 minutes)

Both Level 1 and Level 2 are configured if no level is specified.

Command Modes

Router configuration

Command History

Release

Modification

Release 3.2

This command was introduced.

Usage Guidelines

The refresh interval determines the rate at which the software periodically sends the route topology information that it originates. This behavior is done to keep the information from becoming too old. By default, the refresh interval is 900 seconds (15 minutes).

LSPs must be refreshed periodically before their lifetimes expire. The refresh interval must be less than the LSP lifetime specified with this router command. Reducing the refresh interval reduces the amount of time that undetected link-state database corruption can persist at the cost of increased link utilization. (This event is extremely unlikely, however, because there are other safeguards against corruption.) Increasing the interval reduces the link utilization caused by the flooding of refreshed packets (although this utilization is very small).

Task ID

Task ID

Operations

isis

read, write

Examples

The following example shows how to change the LSP refresh interval to 10,800 seconds (3 hours):

Related Commands

maximum-paths (IS-IS)

To configure the maximum number of parallel routes that an IP routing protocol will install into the routing table, use the maximum-paths command in address family configuration mode. To remove the maximum-paths command from the configuration file and restore the system to its default condition with respect to the routing protocol, use the no form of this command.

maximum-pathsmaximum

nomaximum-paths

Syntax Description

maximum

Maximum number of parallel routes that IS-IS can install in a routing table. Range is 1 to 16

Command Default

maximum: 8 routes

Command Modes

Address family configuration

Command History

Release

Modification

Release 3.2

This command was introduced.

Usage Guidelines

Task ID

Task ID

Operations

isis

read, write

Examples

The following example shows how to allow a maximum of 16 paths to a destination:

maximum-redistributed-prefixes (IS-IS)

To specify an upper limit on the number of redistributed prefixes (subject to summarization) that the Intermediate System-to-Intermediate System (IS-IS) protocol advertises, use the maximum-redistributed-prefixes command in address family mode. To disable this feature, use the no form of this command.

maximum-redistributed-prefixesmaximum
[ level
{ 1 | 2 } ]

nomaximum-redistributed-prefixes
[ maximum
[ level
{ 1 | 2 } ] ]

Syntax Description

maximum

Maximum number of redistributed prefixes advertised. Range is 1 to 28000.

level {1 | 2}

(Optional) Specifies maximum prefixes for Level 1 or Level 2.

Command Default

maximum: 10000

level: 1-2

Command Modes

Address family configuration

Command History

Release

Modification

Release 3.2

This command was introduced.

Usage Guidelines

Use the maximum-redistributed-prefixes command to prevent a misconfiguration from resulting in redistribution of excess prefixes. If IS-IS encounters more than the maximum number of prefixes, it sets a bi-state alarm. If the number of to-be-redistributed prefixes drops back to the maximum or lower—either through reconfiguration or a change in the redistribution source—IS-IS clears the alarm.

Task ID

Task ID

Operations

isis

read, write

Examples

The following example shows how to specify the number of redistributed prefixes at 5000 for Level 2:

max-lsp-lifetime

To set the maximum time that link-state packets (LSPs) persist without being refreshed, use the max-lsp-lifetime command in router configuration mode. To restore the default time, use the no form of this command.

max-lsp-lifetimeseconds
[ level
{ 1 | 2 } ]

nomax-lsp-lifetime
[ seconds
[ level
{ 1 | 2 } ] ]

Syntax Description

seconds

Lifetime (in seconds) of the LSP. Range from 1 to 65535 seconds.

level {1 | 2}

(Optional) Specifies routing Level 1 or Level 2 independently.

Command Default

seconds: 1200 seconds (20 minutes)

Both Level 1 and Level 2 are configured if no level is specified.

Command Modes

Router configuration

Command History

Release

Modification

Release 3.2

This command was introduced.

Usage Guidelines

You might need to adjust the maximum LSP lifetime if you change the LSP refresh interval with the lsp-refresh-interval command. The maximum LSP lifetime must be greater than the LSP refresh interval.

Task ID

Task ID

Operations

isis

read, write

Examples

The following example shows how to set the maximum time that the LSP persists to 11,000 seconds (more than 3 hours):

Related Commands

mesh-group (IS-IS)

To optimize link-state packet (LSP) flooding in highly meshed networks, use the mesh-group command in interface configuration mode. To remove a subinterface from a mesh group, use the no form of this command.

mesh-group
{ number | blocked }

nomesh-group

Syntax Description

number

Number identifying the mesh group of which this interface is a member. Range is 1 to 4294967295.

blocked

Specifies that no LSP flooding takes place on this interface.

Command Default

There is no mesh group configuration (normal LSP flooding).

Command Modes

Interface configuration

Command History

Release

Modification

Release 3.2

This command was introduced.

Usage Guidelines

LSPs first received on subinterfaces that are not part of a mesh group are flooded to all other subinterfaces in the usual way.

LSPs first received on subinterfaces that are part of a mesh group are flooded to all interfaces except those in the same mesh group. If the blocked keyword is configured on a subinterface, then a newly received LSP is not flooded out over that interface.

To minimize the possibility of incomplete flooding, you should allow unrestricted flooding over at least a minimal set of links in the mesh. Selecting the smallest set of logical links that covers all physical paths results in very low flooding, but less robustness. Ideally you should select only enough links to ensure that LSP flooding is not detrimental to scaling performance, but enough links to ensure that under most failure scenarios, no router is logically disconnected from the rest of the network. In other words, blocking flooding on all links permits the best scaling performance, but there is no flooding. Permitting flooding on all links results in very poor scaling performance.

Note

See RFC 2973 for details about the mesh group specification.

Task ID

Task ID

Operations

isis

read, write

Examples

In the following example, six interfaces are configured in three mesh groups. LSPs received are handled as follows:

LSPs first received by GigabitEthernet interface 0/1/0/0 are flooded to all interfaces except GigabitEthernet 0/1/0/1 (which is part of the same mesh group) and GigabitEthernet 0/3/0/0 (which is blocked).

LSPs first received by GigabitEthernet 0/2/0/1 are flooded to all interfaces except GigabitEthernet 0/2/0/0 (which is part of the same mesh group) and GigabitEthernet 0/3/0/0 (which is blocked).

LSPs first received by GigabitEthernet 0/3/0/0 are not ignored, but flooded as usual to all interfaces.

LSPs received first through GigabitEthernet 0/3/0/1 are flooded to all interfaces, except GigabitEthernet 0/3/0/0 (which is blocked).

metric (IS-IS)

To configure the metric for an Intermediate System-to-Intermediate System (IS-IS) interface, use the metric command in address family or interface address family configuration mode. To restore the default metric value, use the no form of this command.

metric
{ default-metric | maximum }
[ level
{ 1 | 2 } ]

nometric
[ { default-metric | maximum }
[ level
{ 1 | 2 } ] ]

Syntax Description

default-metric

Metric assigned to the link and used to calculate the cost from each other router using the links in the network to other destinations. Range is 1 to 63 for narrow metric and 1 to 16777214 for wide metric.

Note

Setting the default metric under address family results in setting the same metric for all interfaces that is associated with the address family. Setting a metric value under an interface overrides the default metric

maximum

Specifies maximum wide metric. All routers exclude this link from their shortest path first (SPF).

Configures the software to generate and accept only new-style TLV objects objects.

metric-style narrow

To configure the Intermediate System-to-Intermediate System (IS-IS) software to generate and accept old-style type, length, and value (TLV) objects, use the metric-style narrow command in address family configuration mode. To remove the metric-style narrow command from the configuration file and restore the system to its default condition, use the no form of this command.

metric-stylenarrow [transition]
[ level
{ 1 | 2 } ]

nometric-stylenarrow [transition]
[ level
{ 1 | 2 } ]

Syntax Description

transition

(Optional) Instructs the router to generate and accept both old-style and new-style TLV objects. It generates only old-style TLV objects.

Related Commands

Configures a router to generate and accept only new-style TLV objects.

metric-style transition

To configure the Intermediate System-to-Intermediate System (IS-IS) software to generate and accept both old-style and new-style type, length, and value (TLV) objects, use the metric-style transition command in address family configuration mode. To remove the metric-style transition command from the configuration file and restore the system to its default condition, use the noform of this command.

metric-styletransition
[ level
{ 1 | 2 } ]

nometric-styletransition
[ level
{ 1 | 2 } ]

Syntax Description

transition

Instructs the router to generate and accept both old-style and new-style TLV objects.

Related Commands

Configures a router to generate and accept only new-style TLV objects.

metric-style wide

To configure the Intermediate System-to-Intermediate System (IS-IS) software to generate and accept only new-style type, length, and value (TLV) objects, use the metric-style wide command in address family configuration mode. To remove the metric-style wide command from the configuration file and restore the system to its default condition, use the no form of this command.

metric-stylewide [transition]
[ level
{ 1 | 2 } ]

nometric-stylewide [transition]
[ level
{ 1 | 2 } ]

Syntax Description

transition

(Optional) Instructs the router to generate and accept both old-style and new-style TLV objects. It generates only new-style TLV objects.

level {1 | 2}

(Optional) Specifies routing Level 1 or Level 2 independently.

Command Default

Old-style TLV lengths are generated, if this command is not configured.

Both Level 1 and Level 2 are configured if no level is specified.

Command Modes

Address family configuration

Command History

Release

Modification

Release 3.2

This command was introduced.

Usage Guidelines

IS-IS traffic engineering extensions include new-style TLV objects with wider metric fields than old-style TLV objects. If you enter the metric-style wide command, a router generates and accepts only new-style TLV objects. Therefore, the router uses less memory and fewer other resources rather than generating both old-style and new-style TLV objects.

This discussion of metric styles and transition strategies is oriented toward traffic engineering deployment. Other commands and models might be appropriate if the new-style TLV objects are desired for other reasons. For example, a network may require wider metrics, but might not use traffic engineering.

Task ID

Task ID

Operations

isis

read, write

Examples

The following example shows how to configure a router to generate and accept only new-style TLV objects on Level 1:

mpls ldp auto-config

To enable Label Distribution Protocol (LDP) Interior Gateway Protocol (IGP) interface auto-configuration, use the mpls ldp auto-config command in IPv4 address family configuration mode. To disable LDP IGP auto-configuration, use the no form of this command.

mplsldpauto-config

nomplsldpauto-config

Syntax Description

This command has no keywords or arguments.

Command Default

LDP IGP auto-configuration is disabled.

Command Modes

IPv4 address family configuration

Command History

Release

Modification

Release 3.5.0

This command was introduced.

Usage Guidelines

Use the mpls ldp auto-config command to automatically configure LDP on a set of interfaces associated with a specified IGP instance. Further, LDP IGP auto-configuration provides a means to block LDP from being enabled on a specified interface. If you do not want an IS-IS interface to have LDP enabled, use the igp auto-config disable command.

Related Commands

Command

Description

igp auto-config disable

Disables LDP IGP auto-configuration for a specific interface.

mpls ldp sync (IS-IS)

To configure Label Distribution Protocol (LDP) IS-IS synchronization, use the mpls ldp sync command in interface address family configuration mode. To disable LDP synchronization, use the no form of this command.

mplsldpsync
[ level
{ 1 | 2 } ]

nomplsldpsync
[ level
{ 1 | 2 } ]

Syntax Description

level {1 | 2}

(Optional) Sets LDP synchronization for the specified level.

Command Default

If a level is not specified, LDP synchronization is set for both levels.

Command Modes

Interface address family configuration

Command History

Release

Modification

Release 3.3.0

This command was introduced.

Usage Guidelines

MPLS VPN traffic forwarded using LDP labels can be dropped in the following instances:

A new link is introduced in the network and IS-IS has converged before LDP establishes labels.

An existing LDP session goes down while IS-IS adjacency is intact over the link.

In both instances, outbound LDP labels are not available for forwarding MPLS traffic. LDP IS-IS synchronization addresses the traffic drop. When the mpls ldp sync command is configured, IS-IS advertises the maximum possible link metric until LDP has converged over the link. The link is less preferred and least used in forwarding MPLS traffic. When LDP establishes the session and exchanges labels, IS-IS advertises the regular metric over the link.

Note

IS-IS advertises the maximum metric –1 (16777214) if wide metrics are configured since the maximum wide metric is specifically used for link exclusion from the shortest path first algorithm (SPF) (RFC 3784). However, the maximum narrow metric is unaffected by this definition.

Related Commands

mpls traffic-eng (IS-IS)

To configure a router running the Intermediate System-to-Intermediate System (IS-IS) protocol to flood Multiprotocol Label Switching traffic engineering (MPLS TE) link information into the indicated IS-IS level, use the mpls traffic-eng command in IPv4 address family configuration mode. To disable this feature, use the no form of this command.

mplstraffic-eng
{ level-1 | level-1-2 | level-2-only }

nomplstraffic-eng
[ level-1 | level-1-2 | level-2-only ]

Syntax Description

level-1

Specifies routing level 1.

level-1-2

Specifies routing levels 1 and 2.

level-2-only

Specifies routing level 2.

Command Default

Flooding is disabled.

Command Modes

IPv4 address family configuration

Command History

Release

Modification

Release 3.2

This command was introduced.

Release 3.4.0

The level {1 | 2} keywords were removed. The following keywords were added:

level-1

level-1-2

level-2-only

Usage Guidelines

Use the mpls traffic-eng command, which is part of the routing protocol tree, to flood link resource information (such as available bandwidth) for appropriately configured links in the link-state packet (LSP) of the router.

Task ID

Task ID

Operations

isis

read, write

Examples

The following example shows how to turn on MPLS traffic engineering for IS-IS level 1:

Related Commands

Specifies that the traffic engineering router identifier for the node is the IP address associated with a given interface.

mpls traffic-eng multicast-intact (IS-IS)

To enable multicast-intact for Intermediate System-to-Intermediate System (IS-IS) routes with Protocol-Independent Multicast (PIM) and Multiprotocol Label Switching (MPLS) traffic engineering, use the mpls traffic-engmulticast-intact command in IPv4 address family configuration mode. To disable this feature, use the no form of this command.

mplstraffic-engmulticast-intact

nomplstraffic-eng [multicast-intact]

Syntax Description

This command has no keywords or arguments.

Command Default

Multicast-intact is disabled.

Command Modes

IPv4 address family configuration

Command History

Release

Modification

Release 3.2

This command was introduced.

Usage Guidelines

If Multiprotocol Label Switching Traffic Engineering (MPLS-TE) is configured through the IS-IS routing domain and multicast protocols (like Protocol Independent Multicast [PIM]) are also enabled, then use the mpls traffic-end multicast-intact command to install nontraffic engineering next hops in the Routing Information Base (RIB) for use by multicast. The installation of IP-only next hops is in addition to the installation of the standard set of paths for a prefix, which might be through traffic engineered tunnels.

The mpls traffic-eng multicast-intact command allows PIM to use the native hop-by-hop neighbors even though the unicast routing is using MPLS TE tunnels.

Examples

The following example shows how to enable the multicast-intact feature:

Related Commands

Displays a list of connected IS-IS routers in all areas, optionally for multicast-intact.

mpls traffic-eng path-selection ignore overload

To ensure that label switched paths (LSPs) are not disabled when routers have the Intermediate System-to-Intermediate System (IS-IS) overload bit set, use the mpls traffic-eng path-selection ignore overload command in global configuration mode. To disable this override, use the no form of this command.

mplstraffic-engpath-selectionignoreoverload

nomplstraffic-engpath-selectionignoreoverload

Command Default

No default behavior or values

Command Modes

Global configuration

Command History

Release

Modification

Release 3.7.0

This command was introduced.

Usage Guidelines

When the IS-IS overload bit avoidance feature is activated, which means that they are still available for use label switched paths (LSPs), all nodes with the overload bit set, including the following nodes, are ignored:

head nodes

mid nodes

tail nodes

Task ID

Task ID

Operations

mpls-te

read, write

Examples

The following example shows how to activate IS-IS overload bit avoidance:

Related Commands

Configures a router to signal other routers not to use it as an intermediate hop in their shortest path first (SPF) calculations.

mpls traffic-eng router-id (IS-IS)

To specify the Multiprotocol Label Switching traffic engineering (MPLS TE) router identifier for the node, use the mpls traffic-eng router-id command in IPv4 address family configuration mode. To disable this feature, use the no form of this command.

mplstraffic-engrouter-id
{ ip-address | typeinterface-path-id }

nomplstraffic-eng [router-id]

Syntax Description

ip-address

IP address in four-part, dotted-decimal notation.

type

Interface type. For more information, use the question mark (?) online help function.

interface-path-id

Physical interface or virtual interface.

Note

Use the showinterfaces command to see a list of all interfaces currently configured on the router.

For more information about the syntax for the router, use the question mark (?) online help function.

Command Default

Global router identifier is used.

Command Modes

IPv4 address family configuration

Command History

Release

Modification

Release 3.2

This command was introduced.

Usage Guidelines

The identifier of the router acts as a stable IP address for the traffic engineering configuration. This IP address is flooded to all nodes. For all traffic engineering tunnels originating at other nodes and ending at this node, you must set the tunnel destination to the traffic engineering router ID of the destination node, because that is the address used by the traffic engineering topology database at the tunnel head for its path calculation.

Note

We recommend that loopback interfaces be used for MPLS TE, because they are more stable than physical interfaces.

Task ID

Task ID

Operations

isis

read, write

Examples

The following example shows how to specify the traffic engineering router identifier as the IP address associated with loopback interface 0:

Related Commands

Turns on flooding of MPLS traffic engineering link information in the indicated IGP level or area.

net

To configure an Intermediate System-to-Intermediate System (IS-IS) network entity title (NET) for the routing instance, use the net command in router configuration mode. To remove the net command from the configuration file and restore the system to its default condition, use the noform of this command.

netnetwork-entity-title

nonetnetwork-entity-title

Syntax Description

network-entity-title

NET that specifies the area address and the system ID for an ISIS routing process.

Command Default

No NET is configured. The IS-IS instance is not operational, because a NET is mandatory.

Command Modes

Router configuration

Command History

Release

Modification

Release 3.2

This command was introduced.

Usage Guidelines

Under most circumstances, one and only one NET should be configured.

A NET is a network service access point (NSAP) where the last byte is always 0. On a Cisco router running IS-IS, a NET can be 8 to 20 bytes in length. The last byte is always the n-selector and must be 0. The n-selector indicates to which transport entity the packet is sent. An n-selector of 0 indicates no transport entity and means that the packet is for the routing software of the system.

The six bytes directly preceding the n-selector are the system ID. The system ID length is a fixed size and cannot be changed. The system ID must be unique throughout each area (Level 1) and throughout the backbone (Level 2).

All bytes preceding the system ID are the area ID.

A maximum of three NETs for each router is allowed. In rare circumstances, it is possible to configure two or three NETs. In such a case, the area this router is in has three area addresses. Only one area still exists, but it has more area addresses.

Configuring multiple NETs can be temporarily useful in network reconfiguration in which multiple areas are merged, or in which one area is split into more areas. Multiple area addresses enable you to renumber an area individually as needed.

Task ID

Task ID

Operations

isis

read, write

Examples

The following example shows how to configure a router with NET area ID 47.0004.004d.0001 and system ID 0001.0c11.1110:

nsf (IS-IS)

To enable nonstop forwarding (NSF) on the next restart, use the nsf command in router configuration mode. To restore the default setting, use the no form of this command.

nsf
{ cisco | ietf }

nonsf
{ cisco | ietf }

Syntax Description

cisco

Specifies Cisco-proprietary NSF restart.

ietf

Specifies Internet Engineering Task Force (IETF) NSF restart.

Command Default

NSF is disabled.

Command Modes

Router configuration

Command History

Release

Modification

Release 3.2

This command was introduced.

Usage Guidelines

NSF allows an Intermediate System-to-Intermediate System (IS-IS) instance to restart using checkpointed adjacency and link-state packet (LSP) information, and to perform restart with no impact on its neighbor routers. In other words, there is no impact on other routers in the network due to the destruction and recreation of adjacencies and the system LSP.

nsf interface-expires

To configure the number of resends of an acknowledged nonstop forwarding (NSF)-restart acknowledgment, use the nsf interface-expires command in router configuration mode. To restore the default value, use the no form of this command.

nsfinterface-expiresnumber

nonsfinterface-expires

Syntax Description

number

Number of resends. Range is 1 to 3.

Command Default

number: 3 resends

Command Modes

Router configuration

Command History

Release

Modification

Release 3.2

This command was introduced.

Usage Guidelines

When a hello packet sent with the NSF restart flag set is not acknowledged, it is re-sent. Use the nsf interface-expires command to control the number of times the NSF hello is re-sent. When this limit is reached on an interface, any neighbor previously known on that interface is assumed to be down and the initial shortest path first (SPF) calculation is permitted, provided that all other necessary conditions are met.

The total time period available for adjacency reestablishment (interface-timer * interface-expires) should be greater than the expected total NSF restart time.

The nsf interface-expires command applies only to Internet Engineering Task Force (IETF)-style NSF. It has no effect if Cisco-proprietary NSF is configured.

Task ID

Task ID

Operations

isis

read, write

Examples

The following example shows how to allow only one retry attempt on each interface if an IETF NSF restart signal is not acknowledged:

Related Commands

Configures the time interval after which an unacknowledged IETF NSF restart attempt is repeated.

nsf interface-timer

To configure the time interval after which an unacknowledged Internet Engineering Task Force (IETF) nonstop forwarding (NSF) restart attempt is repeated, use the nsf interface-timer command in router configuration mode. To restore the default value, use the no form of this command.

nsfinterface-timerseconds

nonsfinterface-timer

Syntax Description

seconds

NSF restart time interval (in seconds). Range is 3 to 20 seconds.

Command Default

seconds: 10 seconds

Command Modes

Router configuration

Command History

Release

Modification

Release 3.2

This command was introduced

Usage Guidelines

When the IETF NSF restart process begins, hello packets send an NSF restart flag that must be acknowledged by the neighbors of the router. Use the nsf interface-timer command to control the restart time interval after the hello packet is re-sent. The restart time interval need not match the hello interval.

The nsf interface-timer command applies only to IETF-style NSF. It has no effect if Cisco proprietary NSF is configured.

Task ID

Task ID

Operations

isis

read, write

Examples

The following example shows how to ensure that a hello packet with the NSF restart flag set is sent again every 5 seconds until the flag is acknowledged:

Related Commands

Specifies the length of time between hello packets that the software sends.

nsf lifetime (IS-IS)

To configure the maximum route lifetime following a nonstop forwarding (NSF) restart, use the nsf lifetime command in router configuration mode. To restore the default value, use the no form of this command.

Syntax Description

Command Default

seconds: 60 seconds (1 minute)

Command Modes

Router configuration

Command History

Release

Modification

Release 3.2

This command was introduced.

Usage Guidelines

Use the nsf lifetime command to set the maximum available time for the reacquisition of checkpointed adjacencies and link-state packets (LSPs) during a Cisco proprietary NSF restart. LSPs and adjacencies not recovered during this time period are abandoned, thus causing changes to the network topology.

Task ID

Task ID

Operations

isis

read, write

Examples

The following example shows how to configure the router to allow only 20 seconds for the entire NSF process:

passive (IS-IS)

To suppress Intermediate System-to-Intermediate System (IS-IS) packets from being transmitted to the interface and received packets from being processed on the interface, use the passive command in interface configuration mode. To restore IS-IS packets coming to an interface, use the no form of this command.

passive

nopassive

Command Default

Interface is active.

Command Modes

Interface configuration

Command History

Release

Modification

Release 3.2

This command was introduced.

Usage Guidelines

Task ID

Task ID

Operations

isis

read, write

Examples

The following example shows how to configure the router to suppress IS-IS packets on GigabitEthernet interface 0/1/0/1:

Related Commands

Allows the IS-IS interface to participate in forming adjacencies without advertising connected prefixes in the LSPs.

point-to-point

To configure a network of only two networking devices that use broadcast media and the integrated Intermediate System-to-Intermediate System (IS-IS) routing protocol to function as a point-to-point link instead of a broadcast link, use the point-to-point command in interface configuration mode. To disable the point-to-point usage, use the no form of this command.

point-to-point

nopoint-to-point

Syntax Description

This command has no keywords or arguments.

Command Default

Interface is treated as broadcast if connected to broadcast media.

Command Modes

Interface configuration

Command History

Release

Modification

Release 3.2

This command was introduced.

Usage Guidelines

Use the point-to-point command only on broadcast media in a network with two networking devices. The command causes the system to issue packets point-to-point rather than as broadcasts. Configure the command on both networking devices in the network.

Task ID

Task ID

Operations

isis

read, write

Examples

The following example shows how to configure a 10-Gb Ethernet interface to act as a point-to-point interface:

priority (IS-IS)

To configure the priority of designated routers, use the priority command in interface configuration mode. To reset the default priority, use the no form of this command.

priorityvalue
[ level
{ 1 | 2 } ]

nopriority [value]
[ level
{ 1 | 2 } ]

Syntax Description

value

Priority of a router. Range is 0 to 127.

level {1 | 2}

(Optional) Specifies routing Level 1 or Level 2 independently.

Command Default

value: 64

Both Level 1 and Level 2 are configured if no level is specified.

Command Modes

Interface configuration

Command History

Release

Modification

Release 3.2

This command was introduced

Usage Guidelines

Priorities can be configured for Level 1 and Level 2 independently. Specifying Level 1 or Level 2 resets priority only for Level 1 or Level 2 routing, respectively. Specifying no level allows you to configure all levels.

The priority is used to determine which router on a LAN is the designated router or Designated Intermediate System (DIS). The priorities are advertised in the hello packets. The router with the highest priority becomes the DIS.

In the Intermediate System-to-Intermediate System (IS-IS) protocol, there is no backup designated router. Setting the priority to 0 lowers the chance of this system becoming the DIS, but does not prevent it. If a router with a higher priority comes online, it takes over the role from the current DIS. For equal priorities, the higher MAC address breaks the tie.

Task ID

Task ID

Operations

isis

read, write

Examples

The following example shows how to give Level 1 routing priority by setting the priority level to 80. This router is now more likely to become the DIS.

propagate level

To propagate routes from one Intermediate System-to-Intermediate System (IS-IS) level into another level, use the propagate level command in address family configuration mode. To disable propagation, use the no form of this command.

Command Default

Command Modes

Command History

The distribute-list access-list-name keyword and argument were changed to route-policyroute-policy-name.

Usage Guidelines

In general, route propagation from Level 1 to Level 2 is automatic. You might want to use this command to better control which Level 1 routes can be propagated into Level 2.

Propagating Level 2 routes into Level 1 is called route leaking. Route leaking is disabled by default. That is, Level 2 routes are not automatically included in Level 1 link-state packets (LSPs). If you want to leak Level 2 routes into Level 1, you must enable that behavior by using this command.

Propagation from Level 1 into Level 1 and from Level 2 into Level 2 is not allowed.

Task ID

Task ID

Operations

isis

read, write

Examples

The following example shows how to redistribute Level 2 routes to Level 1:

Related Commands

Redistributes routes from one routing domain into a specified IS-IS instance.

redistribute (IS-IS)

To redistribute routes from one routing protocol into Intermediate System-to-Intermediate System (IS-IS), use the redistribute command in address family configuration mode. To remove the redistribute command from the configuration file and restore the system to its default condition in which the software does not redistribute routes, use the no form of this command.

Syntax Description

For the bgp keyword, an autonomous system number has the following ranges:

Range for 2-byte Autonomous system numbers (ASNs) is 1 to 65535.

Range for 4-byte Autonomous system numbers (ASNs) in asplain format is 1 to 4294967295.

Range for 4-byte Autonomous system numbers (ASNs) is asdot format is 1.0 to 65535.65535.

For the isis keyword, an IS-IS instance identifier from which routes are to be redistributed.

For the ospf keyword, an OSPF process name from which routes are to be redistributed. The value takes the form of a string. A decimal number can be entered, but it is stored internally as a string.

For the ospfv3 keyword, an OSPFv3 process name from which routes are to be redistributed. The value takes the form of a string. A decimal number can be entered, but it is stored internally as a string.

level-1

(Optional) Specifies that redistributed routes are advertised in the Level-1 LSP of the router.

level-1-2

(Optional) Specifies that redistributed routes are advertised in the Level-1-2 LSP of the router.

level-2

(Optional) Specifies that redistributed routes are advertised in the Level-2 LSP of the router.

metric metric-value

(Optional) Specifies the metric used for the redistributed route. Range is 0 to 16777215. The metric-value must be consistent with the IS-IS metric style of the area and topology into which the routes are being redistributed.

(Optional) Specifies the external link type associated with the route advertised into the ISIS routing domain. It can be one of four values:

external

internal–Use the internal keyword to set IS-IS internal metric-type

external –Use the external keyword to set IS-IS external metric-type

rib-metric-as-external–Use the rib-metric-as-external keyword to use RIB metric and set IS-IS external metric-type

rib-metric-as-internal–Use the rib-metric-as-internal keyword to use RIB metric and set IS-IS internal metric-type

Any route with an internal metric (however large the metric is) is preferred over a route with external metric (however small the metric is).

Use the rib-metric-as-external and rib-metric-as-internal keywords to preserve RIB metrics when redistributing routes from another IS-IS router instance or another protocol.

route-policy route-policy-name

(Optional) Specifies the identifier of a configured policy. A policy is used to filter the importation of routes from this source routing protocol to IS-IS.

match {internal | external [1 | 2] | nsaa-external [1 | 2]}

(Optional) Specifies the criteria by which OSPF routes are redistributed into other routing domains. It can be one or more of the following:

internal—Routes that are internal to a specific autonomous system (intra- and interarea OSPF routes).

external [1 | 2]—Routes that are external to the autonomous system, but are imported into OSPF as Type 1 or Type 2 external routes.

nssa-external [1 | 2]—Routes that are external to the autonomous system, but are imported into OSPF as Type 1 or Type 2 not-so-stubby area (NSSA) external routes.

For the external and nssa-external options, if a type is not specified, then both Type 1 and Type 2 are assumed.

Command Default

Level 2 is configured if no level is specified.

metric-type: internal

match: If no match keyword is specified, all OSPF routes are redistributed.

Command Modes

Address family configuration

Command History

Release

Modification

Release 3.2

This command was introduced.

Release 3.3.0

The policy policy-name keyword and argument were changed to route-policy route-policy-name.

Release 3.8.0

The rib-metric-as-external and rib-metric-as-internal keywords were added.

Release 3.9.0

Asplain format for 4-byte Autonomous system numbers notation was supported.

Usage Guidelines

Note

When redistributing routes (into IS-IS) using both command keywords for setting or matching of attributes and a route policy, the routes are run through the route policy first, followed by the keyword matching and setting.

Use the redistribute command to control the redistribution of routes between separate IS-IS instances. To control the propagation of routes between the levels of a single IS-IS instance, use the propagate level command.

Only IPv4 OSPF addresses can be redistributed into IS-IS IPv4 address families and only IPv6 OSPFv3 prefixes can be distributed into IS-IS IPv6 address families.

Task ID

Task ID

Operations

isis

read, write

Examples

In this example, IS-IS instance isp_A readvertises all of the routes of IS-IS instance isp_B in Level 2 LSP. Note that the level-2 keyword affects which levels instance isp_A advertises the routes in and has no impact on which routes from instance isp_B are advertised. (Any Level 1 routes from IS-IS instance isp_B are included in the redistribution.

Related Commands

retransmit-interval (IS-IS)

To configure the amount of time between retransmission of each Intermediate System-to-Intermediate System (IS-IS) link-state packet (LSP) on a point-to-point link, use the retransmit-interval command in interface configuration mode. To restore the default value, use the no form of this command.

retransmit-intervalseconds
[ level
{ 1 | 2 } ]

noretransmit-interval
[ seconds
[ level
{ 1 | 2 } ] ]

Syntax Description

seconds

Time (in seconds) between consecutive retransmissions of each LSP. It is an integer that should be greater than the expected round-trip delay between any two networking devices on the attached network. Range is 0 to 65535 seconds.

level {1 | 2}

(Optional) Specifies routing Level 1 or Level 2 independently.

Command Default

seconds: 5 seconds

Command Modes

Interface configuration

Command History

Release

Modification

Release 3.2

This command was introduced.

Usage Guidelines

To prevent needless transmission results, the seconds argument should be conservative.

The retransmit-interval command has no effect on LAN (multipoint) interfaces. On point-to-point links, the value can be increased to enhance network stability.

Because retransmissions occur only when LSPs are dropped, setting this command to a higher value has little effect on reconvergence. The more neighbors networking devices have, and the more paths over which LSPs can be flooded, the higher this value can be made.

Task ID

Task ID

Operations

isis

read, write

Examples

The following example shows how to configure GigabitEthernet interface 0/2/0/1 for retransmission of IS-IS LSPs every 60 seconds for a large serial line:

Related Commands

Configures the amount of time between retransmissions of any IS-IS LSPs on a point-to-point interface.

retransmit-throttle-interval

To configure minimum interval between retransmissions of different Intermediate System-to-Intermediate System (IS-IS) link-state packets (LSPs) on a point-to-point interface, use the retransmit-throttle-interval command in interface configuration mode. To remove the command from the configuration file and restore the system to its default condition, use the noform of this command.

retransmit-throttle-intervalmilliseconds
[ level
{ 1 | 2 } ]

noretransmit-throttle-interval
[ milliseconds
[ level
{ 1 | 2 } ] ]

Syntax Description

milliseconds

Minimum delay (in milliseconds) between LSP retransmissions on the interface. Range is 0 to 65535.

level {1 | 2}

(Optional) Specifies routing Level 1 or Level 2 independently.

Command Default

Default is 0.

Command Modes

Interface configuration

Command History

Release

Modification

Release 3.2

This command was introduced.

Usage Guidelines

Use the retransmit-throttle-interval command to define the minimum period of time that must elapse between retransmitting any two consecutive LSPs on an interface. The retransmit-throttle-interval command may be useful in very large networks with many LSPs and many interfaces as a way of controlling LSP retransmission traffic. This command controls the rate at which LSPs can be re-sent on the interface.

Task ID

Task ID

Operations

isis

read, write

Examples

The following example shows how to configure GigabitEthernet interface 0/2/0/1 to limit the rate of LSP retransmissions to one every 300 milliseconds:

Related Commands

Configures the amount of time between retransmission of each IS-IS LSP over a point-to-point link.

router isis

To enable the Intermediate System-to-Intermediate System (IS-IS) routing protocol and to specify an IS-IS instance, use the router isis command in global configuration mode. To disable IS-IS routing, use thenoform of this command.

routerisisinstance-id

norouterisisinstance-id

Syntax Description

instance-id

Name of the routing process. Maximum number of characters is 40.

Command Default

An IS-IS routing protocol is not enabled.

Command Modes

Global configuration

Command History

Release

Modification

Release 3.2

This command was introduced.

Usage Guidelines

Use the router isis command to create an IS-IS routing process. An appropriate network entity title (NET) must be configured to specify the address of the area (Level 1) and system ID of the router. Routing must be enabled on one or more interfaces before adjacencies may be established and dynamic routing is possible.

Multiple IS-IS processes can be configured. Up to eight processes are configurable. A maximum of five IS-IS instances on a system are supported.

Related Commands

set-attached-bit

To configure an Intermediate System-to-Intermediate System (IS-IS) instance with an attached bit in the Level 1 link-state packet (LSP), use the set-attached-bit command in address family configuration mode. To remove the set-attached-bit command from the configuration file and restore the system to its default condition, use the no form of this command.

set-attached-bit

noset-attached-bit

Command Default

Attached bit is not set in the LSP.

Command Modes

Address family configuration

Command History

Usage Guidelines

Use the set-attached bit command to set an IS-IS instance with an attached bit in the Level 1 LSP that allows another IS-IS instance to redistribute Level 2 topology. The attached bit is used when the Level 2 connectivity from another IS-IS instance is advertised by the Level 1 attached bit.

Cisco IOS XR software does not support multiple Level 1 areas in a single IS-IS routing instance. But the equivalent functionality is achieved by redistribution of routes between two IS-IS instances by using the redistribute (IS-IS) command.

The attached bit is configured for a specific address family only if the single-topology command is not configured.

Note

If connectivity for the Level 2 instance is lost, the attached bit in the Level 1 instance LSP continues sending traffic to the Level 2 instance and causes the traffic to be dropped.

Task ID

Task ID

Operations

isis

read, write

Examples

The following example shows how to set the attached bit for a Level 1 instance that allows the Level 2 instance to redistribute routes from the Level 1 instance:

Related Commands

set-overload-bit

To configure the router to signal other routers not to use it as an intermediate hop in their shortest path first (SPF) calculations, use the set-overload-bit command in router configuration mode. To remove the designation, use the noform of this command.

Command Default

Command Modes

Router configuration

Command History

Release

Modification

Release 3.2

This command was introduced.

Usage Guidelines

Use the set-overload-bit command to force the router to set the overload bit in its nonpseudonode link-state packets (LSPs). Normally the setting of the overload bit is allowed only when a router experiences problems. For example, when a router is experiencing a memory shortage, the reason might be that the link-state database is not complete, resulting in an incomplete or inaccurate routing table. If the overload bit is set in the LSPs of the unreliable router, other routers can ignore the router in their SPF calculations until it has recovered from its problems. The result is that no paths through the unreliable router are seen by other routers in the Intermediate System-to-Intermediate System (IS-IS) area. However, IP prefixes directly connected to this router are still reachable.

The set-overload-bit command can be useful when you want to connect a router to an IS-IS network, but do not want real traffic flowing through it under any circumstances.

Routers with overload bit set are:

A test router in the lab, connected to a production network.

A router configured as an LSP flooding server, for example, on a nonbroadcast multiaccess (NBMA) network, in combination with the mesh group feature.

Syntax Description

The instance-id argument is the instance identifier (alphanumeric) defined by the router isis command.

Command Default

No instance ID specified displays IS-IS adjacencies for all the IS-IS instances.

Command Modes

EXEC

Command History

Release

Modification

Release 3.2

This command was introduced.

Usage Guidelines

For each instance, the first line of output lists the IS-IS instance ID with the following lines identifying the IS-IS system ID, supported levels (level 1, level 2, or level-1-2), configured area addresses, active area addresses, status (enabled or not) and type (Cisco or IETF) of nonstop forwarding (NSF), and the mode in which the last IS-IS process startup occurred.

Next, the status of each configured address family (or just IPv4 unicast if none are configured) is summarized. For each level (level 1 or level 2), the metric style (narrow or wide) generated and accepted is listed along with the status of incremental shortest path first (iSPF) computation (enabled or not). Then redistributed protocols are listed, followed by the administrative distance applied to the redistributed routes.

Finally, the running state (active, passive, or disabled) and configuration state (active or disabled) of each IS-IS interface is listed.

Status (enabled or not) and type (Cisco or IETF) of nonstop forwarding (NSF).

Most recent startup mode

The mode in which the last IS-IS process startup occurred.

Topologies supported by IS-IS

The summary of the status of each configured address family (or just IPv4 unicast if none are configured).

Redistributed protocols

List of redistributed protocols, followed by the administrative distance applied to the redistributed routes.

Metric style (generate/accept)

The status of each configured address family (or just IPv4 unicast if none are configured) is summarized. For each level (level 1 or level 2), the metric style (narrow or wide) generated and accepted is listed along with the status of incremental shortest path first (iSPF) computation (enabled or not).

Interfaces supported by IS-IS

The running state (active, passive, or disabled) and configuration state (active or disabled) of each IS-IS interface.

show isis adjacency

To display Intermediate System-to-Intermediate System (IS-IS) adjacencies, use the show isis adjacency command in EXEC mode.

Dynamic hostname of the system. The hostname is specified using the hostname command. If the dynamic hostname is not known or the hostname dynamic disable command has been executed, the 6-octet system ID is used.

Interface

Interface used to reach the neighbor.

SNPA

Data-link address (also known as the Subnetwork Point of Attachment [SNPA]) of the neighbor.

State

Adjacency state of the neighboring interface. Valid states are Down, Init, and Up.

Holdtime

Hold time of the neighbor.

Changed

Time the neighbor has been up (in hours:minutes:seconds).

NSF

Specifies whether the neighbor can adhere to the IETF-NSF restart mechanism.

Syntax Description

The instance-id argument is the instance identifier (alphanumeric) defined by the router isis command.

Command Default

No instance ID specified displays IS-IS checkpoint adjacencies for all the IS-IS instances.

Command Modes

EXEC

Command History

Release

Modification

Release 3.2

This command was introduced.

Usage Guidelines

Use the show isis checkpoint adjacency command to display the checkpointed adjacencies. With this information you can restore the adjacency database during a Cisco proprietary nonstop forwarding (NSF) restart. This command, with the show isis adjacency command, can be used to verify the consistency of the two databases.

Task ID

Task ID

Operations

isis

read

Examples

The following is sample output from the show isis checkpoint adjacency command:

Dynamic hostname of the system. The hostname is specified using the hostname command. If the dynamic hostname is not known or hostname dynamic disable command has been executed, the 6-octet system ID is used.

Syntax Description

The instance-id argument is the instance identifier (alphanumeric) defined by the router isis command.

Command Default

No instance ID specified displays IS-IS checkpoint LSPs for all the IS-IS instances.

Command Modes

EXEC

Command History

Release

Modification

Release 3.2

This command was introduced.

Usage Guidelines

The checkpointed LSPs displayed by this command are used to restore the LSP database during a Cisco-proprietary nonstop forwarding (NSF) restart. The show isis checkpoint lsp command, with the show isis database command, may be used to verify the consistency of the two databases.

Task ID

Task ID

Operations

isis

read

Examples

The following is sample output from the show isis checkpoint lsp command:

LSP identifier. The first six octets form the system ID of the router that originated the LSP.

The next octet is the pseudonode ID. When this byte is zero, the LSP describes links from the system. When it is nonzero, the LSP is a so-called nonpseudonode LSP. This is similar to a router link-state advertisement (LSA) in the Open Shortest Path First (OSPF) protocol. The LSP describes the state of the originating router.

For each LAN, the designated router for that LAN creates and floods a pseudonode LSP, describing all systems attached to that LAN.

The last octet is the LSP number. If there is more data than can fit in a single LSP, the LSP is divided into multiple LSP fragments. Each fragment has a different LSP number. An asterisk (*) indicates that the LSP was originated by the system on which this command is issued.

Command Modes

Command History

Usage Guidelines

Each of the options for the show isis database command can be entered in an arbitrary string within the same command entry. For example, the following are both valid command specifications and provide the same output: show isis database detail level 2 and show isis database level 2 detail.

The summary keyword used with this command allows you to filter through a large IS-IS database and quickly identify problematic areas.

Task ID

Task ID

Operations

isis

read

Examples

The following is sample output from the show isis database command with the summary keyword:

Attach bit (ATT). Indicates that the router is also a Level 2 router, and it can reach other areas. Level 1-only routers and Level 1-2 routers that have lost connection to other Level 2 routers use the Attach bit to find the closest Level 2 router. They point to a default route to the closest Level 2 router.

OVL bit set LSPs

Overload bit. Indicates if the IS is congested. If the Overload bit is set, other routers do not use this system as a transit router when calculating routers. Only packets for destinations directly connected to the overloaded router are sent to this router.

The following is sample output from the
show isis database command with the keyword specified:

As the output shows, besides the information displayed with the show isis database command, the command with the keyword displays the contents of each LSP.

Table 8 show isis database verbose Field Descriptions

Field

Description

LSPID

LSP identifier. The first six octets form the system ID of the router that originated the LSP.

The next octet is the pseudonode ID. When this byte is zero, the LSP describes links from the system. When it is nonzero, the LSP is a so-called nonpseudonode LSP. This is similar to a router link-state advertisement (LSA) in the Open Shortest Path First (OSPF) protocol. The LSP describes the state of the originating router.

For each LAN, the designated router for that LAN creates and floods a pseudonode LSP, describing all systems attached to that LAN.

The last octet is the LSP number. If there is more data than can fit in a single LSP, the LSP is divided into multiple LSP fragments. Each fragment has a different LSP number. An asterisk (*) indicates that the LSP was originated by the system on which this command is issued.

LSP Seq Num

Sequence number for the LSP that allows other systems to determine if they have received the latest information from the source.

LSP Checksum

Checksum of the entire LSP packet.

LSP Holdtime

Time the LSP remains valid (in seconds). An LSP hold time of zero indicates that this LSP was purged and is being removed from the link-state database (LSDB) of all routers. The value indicates how long the purged LSP stays in the LSDB before being completely removed.

ATT/P/OL

ATT—Attach bit. This bit indicates that the router is also a Level 2 router, and it can reach other areas. Level 1-only routers and Level 1-2 routers that have lost connection to other Level 2 routers use the Attach bit to find the closest Level 2 router. They point to a default route to the closest Level 2 router.

P—P bit. Detects if the intermediate system is area partition repair capable. Cisco and other vendors do not support area partition repair.

OL—Overload bit. Determines if the IS is congested. If the Overload bit is set, other routers do not use this system as a transit router when calculating routers. Only packets for destinations directly connected to the overloaded router are sent to this router.

Area Address

Reachable area addresses from the router. For Level 1 LSPs, these are the area addresses configured manually on the originating router. For Level 2 LSPs, these are all the area addresses for the area to which this route belongs.

NLPID

Network Layer Protocol Identifier.

Hostname

Hostname of the node.

IP Address

IP address of the node.

Metric

IS-IS metric for the cost of the adjacency between the originating router and the advertised neighbor, or the metric of the cost to get from the advertising router to the advertised destination (which can be an IP address, an end system (ES), or a Connectionless Network Service (CLNS) prefix).

MPLS SRLG

MPLS SRLG TLV information per neighbor, identified by hostname or system ID.

Interface IP Address

Local interface IP address.

Neighbor IP Address

Remote interface IP address.

Flags

Flags carried in SRLG TLV. The Least Significant Bit (LSB) is set if the interface is numbered.

SRLGs

SRLG values.

show isis database-log

To display the entries in the Intermediate System-to-Intermediate System (IS-IS) database log, use the show isis database-log command in EXEC mode.

LSP identifier. The first six octets form the system ID of the router that originated the LSP.

The next octet is the pseudonode ID. When this byte is zero, the LSP describes links from the system. When it is nonzero, the LSP is a so-called nonpseudonode LSP. This is similar to a router link-state advertisement (LSA) in the Open Shortest Path First (OSPF) protocol. The LSP describes the state of the originating router.

For each LAN, the designated router for that LAN creates and floods a pseudonode LSP, describing all systems attached to that LAN.

The last octet is the LSP number. If there is more data than can fit in a single LSP, the LSP is divided into multiple LSP fragments. Each fragment has a different LSP number. An asterisk (*) indicates that the LSP was originated by the system on which this command is issued.

New LSP

New router or pseudonode appearing in the topology.

Old LSP

Old router or pseudonode leaving the topology.

Op

Operation on the database: inserted (INS) or replaced (REP).

Seq Num

Sequence number for the LSP that allows other systems to determine if they have received the latest information from the source.

Holdtime

Time the LSP remains valid (in seconds). An LSP hold time of 0 indicates that this LSP was purged and is being removed from the link-state database (LSDB) of all routers. The value indicates how long the purged LSP stays in the LSDB before being completely removed.

OL

Overload bit. Determines if the IS is congested. If the Overload bit is set, other routers do not use this system as a transit router when calculating routers. Only packets for destinations directly connected to the overloaded router are sent to this router.

Dynamic hostname of the system. The hostname is specified using the hostname command. If the dynamic hostname is not known or hostname dynamic disable command has been executed, the 6-octet system ID is used.

Status of Bidirectional Forwarding Detection (BFD), either enabled or disabled.

BFD Min Interval:

BFD minimum interval.

BFD Multiplier:

BFD multiplier.

Circuit Type:

Levels the interface is running on (circuit-type configuration) which may be a subset of levels on the router.

Media Type:

Media type on which IS-IS is running.

Circuit Number:

Unique ID assigned to a circuit internally (8-bit integer).

Extended Circuit Number:

Valid only for point-to-point interfaces (32-bit integer).

LSP Rexmit Queue Size:

Number of LSPs pending retransmission on the interface.

Adjacency Count:

Number of adjacencies formed with a neighboring router that supports the same set of protocols.

PSNP Entry Queue Size:

Number of SNP entries pending inclusion in the next PSNP.

LAN ID:

ID of the LAN.

Priority (Local/DIS):

Priority of this interface or priority of the Designated Intermediate System.

Next LAN IIH in:

Time (in seconds) in which the next LAN hello message is sent.

LSP Pacing Interval:

Interval at which the link-state packet (LSP) transmission rate (and by implication the reception rate of other systems) is to be reduced.

Protocol State:

Running state of the protocol (up or down).

MTU:

Link maximum transmission unit (MTU).

SNPA:

Data-link address (also known as the Subnetwork Point of Attachment [SNPA]) of the neighbor.

All Level-n ISs:

Status of interface membership in Layer 2 multicast group. The status options are Yes or reason for not being a member of the multicast group.

IPv4 Unicast Topology:

Status of the topology, either enabled or disabled.

Adjacency Formation:

Status of adjacency formation. The status options are Running or a reason for not being ready to form adjacencies.

Prefix Advertisement:

Status of advertising prefixes, either enabled or disabled.

Metric (L1/L2):

IS-IS metric for the cost of the adjacency between the originating router and the advertised neighbor, or the metric of the cost to get from the advertising router to the advertised destination (which can be an IP address, an end system (ES), or a connectionless network service (CLNS) prefix).

MPLS LDP Sync (L1/L2)

Status of LDP IS-IS synchronization, either enabled or disabled. When enabled, the state of synchronization (Sync Status) is additionally displayed as either achieved or not achieved.

IPv4 Address Family:

Status of the address family, either enabled or disabled.

Protocol State:

State of the protocol.

Forwarding Address(es):

Addresses on this interface used by the neighbor for next-hop forwarding.

Global Prefix(es):

Prefixes for this interface included in the LSP.

LSP transmit timer expires in

LSP transmission expiration timer interval (in milliseconds).

LSP transmission is

State of LSP transmission. Valid states are:

idle

in progress

requested

requested and in progress

The following is sample output from the show isis interface command with the brief keyword:

How long ago (in hh:mm:ss) an LSP rebuild occurred. The last 20 occurrences are logged.

Count

Number of events that triggered this LSP run. When there is a topology change, often multiple LSPs are received in a short period. A router waits 5 seconds before running a full LSP, so it can include all new information. This count denotes the number of events (such as receiving new LSPs) that occurred while the router was waiting its 5 seconds before running full LSP.

Interface

Interface that corresponds to the triggered reasons for the LSP rebuild.

Triggers

A list of all reasons that triggered an LSP rebuild. The triggers are:

AREASET—area set changed

ATTACHFLAG—bit attached

CLEAR—clear command

CONFIG—configuration change

DELADJ—adjacency deleted

DIS—DIS changed

IFDOWN—interface down

IPADDRCHG—IP address change

IPDEFORIG—IP def-orig

IPDOWN—connected IP down

IFDOWN—interface down

IPEXT—external IP

IPIA—nterarea IP

IPUP—connected IP up

LSPDBOL—LSPDBOL bit

LSPREGEN—LSP regeneration

NEWADJ— new adjacency

show isis mesh-group

To display Intermediate System-to-Intermediate System (IS-IS) mesh group information, use the show isis mesh-group command in EXEC mode.

showisis
[ instanceinstance-id ]
mesh-group

Syntax Description

instanceinstance-id

(Optional) Displays the mesh group information for the specified IS-IS instance only.

The instance-id argument is the instance identifier (alphanumeric) defined by the router isis command.

Command Default

No instance ID specified displays the IS-IS mesh group information for all the IS-IS instances.

Command Modes

EXEC

Command History

Release

Modification

Release 3.2

This command was introduced.

Usage Guidelines

Task ID

Task ID

Operations

isis

read

Examples

The following is sample output from the show isis mesh-group command with the instance and instance-id values specified:

Mesh group number to which this interface is a member. A mesh group optimizes link-state packet (LSP) flooding in nonbroadcast multiaccess (NBMA) networks with highly meshed, point-to-point topologies. LSPs that are first received on interfaces that are part of a mesh group are flooded to all interfaces except those in the same mesh group.

GigabitEthernet0/4/0/1

Interface belonging to mesh group 6.

show isis mpls traffic-eng adjacency-log

To display a log of Multiprotocol Label Switching traffic engineering (MPLS TE) adjacency changes for an Intermediate System-to-Intermediate System (IS-IS) instance, use the show isis mpls traffic-eng adjacency-log command in EXEC mode.

Related Commands

show isis mpls traffic-eng advertisements

To display the latest flooded record from Multiprotocol Label Switching traffic engineering (MPLS TE) for an Intermediate System-to-Intermediate System (IS-IS) instance, use the show isis mpls traffic-eng advertisements command in EXEC mode.

showisis
[ instanceinstance-id ]
mplstraffic-engadvertisements

Syntax Description

instanceinstance-id

(Optional) Displays the latest flooded record from MPLS TE for the specified IS-IS instance only.

The instance-id argument is the instance identifier (alphanumeric) defined by the router isis command.

Command Default

No instance ID specified displays the latest flooded record from MPLS TE for all the IS-IS instances.

Command Modes

EXEC

Command History

Release

Modification

Release 3.2

This command was introduced.

Usage Guidelines

Use the show isis mpls traffic-eng advertisements command to verify that MPLS TE is flooding its record and that the bandwidths are correct.

Task ID

Task ID

Operations

isis

read

Examples

The following is sample output from the show isis mpls traffic-eng advertisements command with the instance and instance-id valuesspecified:

Dynamic hostname of the system. The hostname is specified using the hostname command. If the dynamic hostname is not known or if the hostname dynamic disable command has been executed, the 6-octet system ID is used.

Router ID

MPLS TE router ID.

Link Count

Number of links that MPLS TE advertised.

Neighbor System ID

System ID of a neighbor number in an area. The six bytes directly preceding the n-selector are the system ID. The system ID length is a fixed size and cannot be changed. The system ID must be unique throughout each area (Level 1) and throughout the backbone (Level 2). In an IS-IS routing domain, each router is represented by a 6-byte hexadecimal system ID. When network administrators maintain and troubleshoot networking devices, they must know the router name and corresponding system ID.

Dynamic hostname of the system. The hostname is specified using the hostname command. If the dynamic hostname is not known or hostname dynamic disable command has been executed, the 6-octet system ID is used.

Tunnel Name

Name of the MPLS TE tunnel interface.

Bandwidth

MPLS TE-specified tunnel bandwidth of the tunnel.

Nexthop

MPLS TE destination IP address of the tunnel.

Metric

MPLS TE metric of the tunnel.

Mode

MPLS TE metric mode of the tunnel. It can be relative or absolute.

show isis neighbors

To display information about Intermediate System-to-Intermediate System (IS-IS) neighbors, use the show isis neighbors command in EXEC mode.

Dynamic hostname of the system. The hostname is specified using the hostname command. If the dynamic hostname is not known or hostname dynamic disable command has been executed, the 6-octet system ID is used.

Interface

Interface through which the neighbor is reachable.

SNPA

Data-link address (also known as the Subnetwork Point of Attachment [SNPA]) of the neighbor.

State

Adjacency state of the neighboring interface. Valid states are: Down, Init, and Up.

Holdtime

Hold time of the neighbor.

Type

Type of adjacency.

IETF-NSF

Specifies whether the neighbor can adhere to the IETF-NSF restart mechanism. Valid states are Capable and Unable.

Area Address(es)

Number of area addresses on this router.

IPv4 Address(es)

IPv4 addresses configured on this router.

Topologies

Address and subaddress families for which IS-IS is configured.

Uptime

Time (in hh:mm:ss) that the neighbor has been up.

IPFRR: LFA Neighbor

IP fast reroute (IPFRR) loop-free alternate (LFA) neighbor.

LFA IPv4 address:

Address of the LFA.

LFA Interface:

LFA interface.

The following is sample output from the show isis neighbors command with the summary keyword specified:

Dynamic hostname of the system. The hostname is specified using the hostname command. If the dynamic hostname is not known or hostname dynamic disable command has been executed, the 6-octet system ID is used.

IS Levels:

IS-IS level of the router.

Manual area address(es)

Area addresses that are manually configured.

Routing for areaaddress(es)

Area addresses for which this router provides the routing.

Non-stop forwarding:

Status and name of nonstop forwarding (NSF).

Process startup mode:

Mode in which the last process startup occurred. Valid modes are:

Cisco Proprietary NSF Restart

IETF NSF Restart

Cold Restart

iSPF status:

State of incremental shortest path first (iSPF) configuration for this IS-IS instance. Four states exist:

Disabled if iSPF has not been configured but is awaiting a full SPF to compile the topology for use by the iSPF algorithm.

Dormant if iSPF has been configured but is awaiting initial convergence before initializing.

Awake if iSPF has been configured but is awaiting a full SPF to compile the topology for use by the iSPF algorithm.

Active if IS-IS is ready to consider using the iSPF algorithm whenever a new route calculation needs to be run.

No protocols redistributed:

No redistributed protocol information exists to be displayed.

Distance:

Administrative distance for this protocol.

show isis route

To display IP reachability information for an Intermediate System-to-Intermediate System (IS-IS) instance, use the show isis route command in EXEC mode.

Syntax Description

The instance-id argument is the instance identifier (alphanumeric) defined by the router isis command.

ipv4

(Optional) Specifies IP Version 4 address prefixes.

ipv6

(Optional) Specifies IP Version 6 address prefixes.

afi-all

(Optional) Specifies all address prefixes.

unicast

(Optional) Specifies unicast address prefixes.

multicast

(Optional) Specifies multicast address prefixes.

topology

(Optional) Specifies IS-IS paths to intermediate systems.

all

(Optional) Specifies all topologies.

topology topo-name

(Optional) Specifies topology table information and name of the topology table.

safi-all

(Optional) Specifies all secondary address prefixes.

ip-address

(Optional) Network IP address about which routing information should be displayed.

mask

(Optional) Network mask specified in either of two ways:

Network mask can be a four-part, dotted decimal address. For example, 255.0.0.0 indicates that each bit equal to 1 means the corresponding address bit is a network address.

Network mask can be indicated as a slash (/) and number. For example, /8 indicates that the first 8 bits of the mask are ones, and the corresponding bits of the address are the network address.

/length

(Optional) Length of the IP prefix. A decimal value that indicates how many of the high-order contiguous bits of the address compose the prefix (the network portion of the address). A slash must precede the decimal value. Range is 0 to 32.

longer-prefixes

(Optional) Displays route and more-specific routes.

summary

(Optional) Displays topology summary information.

multicast-intact

(Optional) Displays multicast intact information for this entry.

systemid

(Optional) Displays multicast information by system ID.

backup

(Optional) Displays backup information for this entry.

detail

(Optional) Displays link-state packet (LSP) details.

Command Default

No instance ID specified displays the IP reachability information for all the IS-IS instances.

Number of milliseconds taken to complete this SPF run. Elapsed time is wall clock time, not CPU time.

Nodes

Number of routers and pseudonodes (LANs) that make up the topology calculated in this SPF run.

Trig Count

Number of events that triggered this SPF run. When there is a topology change, often multiple link-state packets (LSPs) are received in a short time. Depending on the configuration of the spf-interval command, a router may wait for a fixed period of time before running a router calculation. This count denotes the number of triggering events that occurred while the router was waiting to run the calculation. For a full description of the triggering events, see List of Triggers.

First Trigger LSP

LSP ID stored by the router whenever a full SPF calculation is triggered by the arrival of a new LSP. The LSP ID can suggest the source of routing instability in an area. If multiple LSPs are causing an SPF run, only the LSP ID of the first received LSP is remembered.

Triggers

List of all reasons that triggered a full SPF calculation. For a list of possible triggers, see List of Triggers.

This table lists triggers of a full SPF calculation.

Table 23 List of Triggers

Trigger

Description

PERIODIC

Runs a full SPF calculation very 15 minutes.

NEWLEVEL

Configured new level (using is-type) on this router.

RTCLEARED

Cleared IS-IS topology on the router.

MAXPATHCHANGE

Changed IP maximum parallel path.

NEWMETRIC

Changed link metric.

ATTACHFLAG

Changed Level 2 Attach bit.

ADMINDIST

Configured another administrative distance for the IS-IS instance on this router.

NEWADJ

Created a new adjacency to another router.

DELADJ

Deleted adjacency.

BACKUP

Installed backup route.

SEEDISPF

Seed incremental SPF.

NEXTHOP

Changed IP next-hop address.

NEWLSP0

New LSP 0 appeared in the topology.

LSPEXPIRED

Some LSP in the link-state database (LSDB) has expired.

LSPHEADER

Changed important LSP header fields.

TLVCODE

Type, length, and value (TLV) objects code mismatch, indicating that different TLV objects are included in the newest version of an LSP.

LINKTV

Changed Link TLV content.

PREFIXTLV

Changed Prefix TLV content.

AREAADDRTLV

Changed Area address TLV content.

IP ADDRTLV

Changed IP address TLV content.

TUNNEL

Changed RRR tunnel.

The following is sample output from the show isis spf-log command with the first keyword specified:

Number of milliseconds taken to complete this SPF run. Elapsed time is wall clock time, not CPU time.

Nodes

Number of routers and pseudonodes (LANs) that make up the topology calculated in this SPF run.

Trig Count

Number of events that triggered this SPF run. When there is a topology change, often multiple link-state packets (LSPs) are received in a short time. Depending on the configuration of the spf-interval command, a router may wait for a fixed period of time before running a router calculation. This count denotes the number of triggering events that occurred while the router was waiting to run the calculation. For a full description of the triggering events, see List of Triggers.

First Trigger LSP

LSP ID stored by the router whenever a full SPF calculation is triggered by the arrival of a new LSP. The LSP ID can suggest the source of routing instability in an area. If multiple LSPs are causing an SPF run, only the LSP ID of the first received LSP is remembered.

Triggers

List of all reasons that triggered a full SPF calculation. For a list of possible triggers, see List of Triggers.

The following is sample output from the show isis spf-log command with the detail keyword specified:

Number of milliseconds taken to complete this SPF run. Elapsed time is wall clock time, not CPU time.

Nodes

Number of routers and pseudonodes (LANs) that make up the topology calculated in this SPF run.

Trig Count

Number of events that triggered this SPF run. When there is a topology change, often multiple link-state packets (LSPs) are received in a short time. Depending on the configuration of the spf-interval command, a router may wait for a fixed period of time before running a router calculation. This count denotes the number of triggering events that occurred while the router was waiting to run the calculation. For a full description of the triggering events, see List of Triggers.

First Trigger LSP

LSP ID stored by the router whenever a full SPF calculation is triggered by the arrival of a new LSP. The LSP ID can suggest the source of routing instability in an area. If multiple LSPs are causing an SPF run, only the LSP ID of the first received LSP is remembered.

Triggers

List of all reasons that triggered a full SPF calculation. For a list of possible triggers, see List of Triggers.

Delay

Two different delays exist:

The delay between the time when the route calculation was first triggered and the time when it was run.

The delay between the end of the last route calculation and the start of this one. This is used to verify that the SPF-interval timers are working correctly, and is only reported for calculations after the first delay.

CPU Time

Two different CPU times exist:

CPU time (in milliseconds) taken to calculate the shortest path tree (SPT).

CPU time (in milliseconds) taken to perform the prefix updates.

Real Time

Two different real times exist:

Real time (in milliseconds) taken to calculate the shortest path tree (SPT).

Real time (in milliseconds) taken to perform the prefix updates.

New LSP Arrivals

Number of LSP arrivals since the start of this route calculation.

Next Wait Interval

Enforced delay until the next route calculation can be run, based on the spf-interval command configuration.

Number of successful lookups (hits) along with the number of lookup attempts (tries). To save time or processing power when receiving multiple copies of the same LSP, IS-IS attempts to look up incoming LSPs to see if they have been received recently.

Fast CSNP cache (hits/tries):

Number of successful lookups (hits) along with the number of lookup attempts (tries). To reduce CSNP construction time, IS-IS maintains a cache of CSNPs and attempts to look up CSNP in this cache before transmission on the interface.

Fast CSNP cache updates:

Number of times the CSNP cache has been updated since the last clearing of statistics. The cache is updated on LSP addition or removal from the database.

LSP checksum errors received:

Number of internal checksum errors received in LSPs.

IIH (LSP/SNP) dropped:

Number of hello, LSP, and SNP messages dropped.

IIH (UPD) Max Queue size:

Maximum number of queued packets.

Average transmit times and rate:

Average time taken to transmit the pdu type across all interfaces and the corresponding rate at which the pdu type is being transmitted.

Average process times and rate:

Average time taken to process an incoming pdu type across all interfaces and the corresponding rate at which the pdu type is being received.

LSPs sourced (new/refresh):

Number of LSPs this IS-IS instance has created or refreshed. To find more details on these LSPs, use the show isis lsp-log command.

SPF calculations:

Number of shortest path first (SPF) calculations. SPF calculations are performed only when the topology changes. They are not performed when external routes change. The interval at which SPF calculations are performed is configured using the spf-interval command.

iSPF calculations:

Number of incremental shortest path first (iSPF) calculations. iSPF calculations are performed only when ISPF has been configured in the isis address family configuration submode.

Partial Route Calculations:

Number of partial route calculations (PRCs). PRCs are processor intensive. Therefore, it may be useful to limit their number, especially how often a PRC is done, especially on slower networking devices. Increasing the PRC interval reduces the processor load on the router, but might slow the rate of convergence. The interval at which PRC calculations are performed is configured using the spf-interval command.

Level-(1/2) (LSPs/CSNPs/PSNPs/Hellos) (sent/rcvd):

Number of LSPs, Complete Sequence Number Packets (CSNPs), Partial Sequence Number Packets (PSNPs), and hello packets sent or received on this interface.

PTP Hellos (sent/rcvd):

Point-to-point (PTP) hellos sent and received.

LSP Retransmissions:

Total number of retransmissions on each IS-IS LSP on a point-to-point interface. The LSP retransmission interval can be configured using the retransmit-throttle-interval command.

Level-(1.2) DRElections:

Total number of Designated Intermediate System elections that have taken place. These counts are maintained on an individual level basis.

LSP Flooding Duplicates:

Number of duplicate LSPs filtered from flooding to the neighbor. In case of parallel interfaces to the same neighbor, IS-IS optimizes the flooding by avoiding sending the same LSP copy on other interfaces.

Dynamic hostname of the system. The hostname is specified using the hostname command. If the dynamic hostname is not known or hostname dynamic disable command has been executed, the 6-octet system ID is used.

Metric

Metric assigned to the link and used to calculate the cost from each router using the links in the network to other destinations. Range is 1 to 16777214. Default is 1 to 63 for narrow metric and 1 to 16777214 for wide metric. 0 is set internally if no metric has been specified by the user.

Next-hop

Address of the next-hop.

Interface

Interface used to reach the neighbor.

SNPA

Data-link address (also known as the Subnetwork Point of Attachment [SNPA]) of the neighbor.

The following is sample output from the show isis topology command with the summary keyword specified:

Dynamic hostname of the system. The hostname is specified using the hostname command. If the dynamic hostname is not known or hostname dynamic disable command has been executed, the 6-octet system ID is used.

shutdown (IS-IS)

To disable the Intermediate System-to-Intermediate System (IS-IS) protocol on a particular interface, use the shutdown command in interface configuration mode. To re-enable the IS-IS protocol, use the no form of this command.

shutdown

noshutdown

Command Default

IS-IS protocol is enabled.

Command Modes

Interface configuration

Command History

Release

Modification

Release 3.2

This command was introduced.

Usage Guidelines

Task ID

Task ID

Operations

isis

read, write

Examples

The following example disables the IS-IS protocol on GigabitEthernet interface 0/1/0/1:

single-topology

To configure the link topology for IP Version 4 (IPv4) when IP Version 6 (IPv6) is configured, use the single-topology command in address family configuration mode. To remove the single-topology command from the configuration file and restore the system to its default condition, use the no form of this command.

single-topology

nosingle-topology

Command Default

Performs in multitopology mode in which independent topologies for IPv4 and IPv6 are running in a single area or domain.

Command Modes

IPv6 address family configuration

Command History

Release

Modification

Release 3.2

This command was introduced.

Usage Guidelines

Use the single-topology command to allow Intermediate System-to-Intermediate System (IS-IS) for IPv6 to be configured on interfaces along with an IPv4 network protocol. All interfaces must be configured with the identical set of network protocols, and all routers in the IS-IS area (for Level 1 routing) or the domain (for Level 2 routing) must support the identical set of network layer protocols on all interfaces.

When single-topology support for IPv6 is being used, only old-style type, length, and value (TLV) objects may be used and a single shortest path (SPF) individual level is used to compute IPv4 (if configured) and IPv6 routes. The use of a single SPF means that both IPv4 IS-IS and IPv6 IS-IS routing protocols must share a network topology.

To allow link information to be shared between IPv4 and IPv6, you must configure the single-topology command for an address family. In single-topology IPv6 mode, the configured metric is always the same for both IPv4 and IPv6.

Task ID

Task ID

Operations

isis

read, write

Examples

The following example shows how to enable single-topology mode for IPv6:

snmp-server traps isis

To enable the Simple Network Management Protocol (SNMP) server notifications (traps) available for IS-IS, use the snmp-server trapsisis command in global configuration mode. To disable all available SNMP notifications, use the no form of this command.

snmp-servertrapsisis
{ all | trapsset }

nosnmp-servertrapsisis
{ all | trapsset }

Syntax Description

all

Specifies all IS-IS SNMP server traps.

traps set

Specify any set of trap names.

Command Default

SNMP server traps notification is disabled.

Command Modes

Router configuration

Command History

Release

Modification

Release 3.8.0

This command was introduced.

Usage Guidelines

Task ID

Task ID

Operations

isis

read, write

Examples

The following examples show how to enable all SNMP server traps available for isis:

Command Default

Command Modes

Command History

Release

Modification

Release 3.2

This command introduced.

Usage Guidelines

SPF calculations are performed only when the topology changes. They are not performed when external routes change.

Use the spf-interval command to control how often the software can perform the SPF calculation. The SPF calculation is processor intensive. Therefore, it may be useful to limit how often this calculation is done, especially when the area is large and the topology changes often. Increasing the SPF interval reduces the processor load of the router, but potentially slows the rate of convergence.

Task ID

Task ID

Operations

isis

read, write

Examples

The following example shows how to set the initial SPF calculation delay to 10 milliseconds and the maximum interval between two consecutive SPF calculations to 5000 milliseconds:

spf prefix-priority (IS-IS)

To assign a priority to an ISIS prefix for customizing the RIB update sequence, use thespf prefix-priority command in address family configuration mode. To restore default values, use the no form of this command.

summary-prefix (IS-IS)

To create aggregate addresses for the Intermediate System-to-Intermediate System (IS-IS) protocol, use the summary-prefix command in address family configuration mode. To restore the default behavior, use the no form of this command.

Syntax Description

address

Summary address designated for a range of IPv4 addresses. The address argument must be in four-part, dotted-decimal notation.

/prefix-length

Length of the IPv4 or IPv6 prefix. A decimal value that indicates how many of the high-order contiguous bits of the address compose the prefix (the network portion of the address). A slash must precede the decimal value.

ipv6-prefix

Summary prefix designated for a range of IPv6 prefixes. The ipv6-prefix argument must be in the form documented in RFC 2373, in which the address is specified in hexadecimal using 16-bit values between colons.

level {1 | 2}

(Optional) Redistributes routes into Level 1 or Level 2 and summarizes them with the configured address and mask value.

tag tag

Sets a tag value. The value range is 1- 4294967295.

Command Default

All redistributed routes are advertised individually.

Both Level 1 and Level 2 are configured if no level is specified.

Command Modes

Address family configuration

Command History

Release

Modification

Release 3.2

This command was introduced.

Release 3.9.0

Tag keyword was added

Usage Guidelines

Multiple groups of addresses can be summarized for a given level. Routes learned from other routing protocols can also be summarized. The metric used to advertise the summary is the smallest metric of all the more-specific routes. Use the summary-prefix command to help reduce the size of the routing table.

This command also reduces the size of the link-state packets (LSPs) and thus the link-state database. It also helps ensure stability, because a summary advertisement depends on many more specific routes. If one more-specific route flaps, in most cases, this flap does not cause a flap of the summary advertisement.

The drawback of summary addresses is that other routes might have less information to calculate the most optimal routing table for all individual destinations.

Note

When IS-IS advertises a summary prefix, it automatically inserts the summary prefix into the IP routing table but labels it as a “discard” route entry. Any packet that matches the entry is discarded to prevent routing loops. When IS-IS stops advertising the summary prefix, the routing table entry is removed.

Task ID

Task ID

Operations

isis

read, write

Examples

The following example shows how to redistribute Open Shortest Path First (OSPF) routes into IS-IS. In the OSPF routing table, IPv6 routes exist for 3ffe:f000:0001:0000::/64, 3ffe:f000:0002:0000::/64, 3ffe:f000:0003:0000::/64, and so on. This example shows only 3ffe:f000::/24 advertised into IPv6 IS-IS Level 2.

suppressed

To allow an IS-IS interface to participate in forming adjacencies without advertising connected prefixes in the system link-state packets (LSPs), use the suppressed command in interface configuration mode. To enable advertising connected prefixes, use the no form of this command.

suppressed

nosuppressed

Command Default

Interface is active.

Command Modes

Interface configuration

Command History

Release

Modification

Release 3.2

This command was introduced.

Usage Guidelines

Use the suppressed command to reduce the number of routes that IS-IS has to maintain, improving convergence times after an isolated failure. Improvement is noticeable if the command is used widely throughout the network. Other routers in the domain do not install routes to the affected connected prefixes.

Task ID

Task ID

Operations

isis

read, write

Examples

The following example shows how to disable the advertisement of connected prefixes on GigabitEthernet interface 0/1/0/1:

Related Commands

tag (IS-IS)

To associate and advertise a tag with the prefix of an IS-IS interface, use the tag command in interface address family configuration mode. To restore the default behavior, use the no form of this command.

tagtag

notag [tag]

Syntax Description

tag

Interface tag. Range is 1 to 4294967295.

Command Default

Default is that no tag is associated and advertised.

Command Modes

Interface address family configuration

Command History

Release

Modification

Release 3.4.0

This command was introduced.

Usage Guidelines

Task ID

Task ID

Operations

isis

read, write

Examples

The following example shows how to associate and advertise an interface tag:

Related Commands

Assigns a priority to an ISIS prefix for customizing the RIB update sequence.

topology-id

To differentiate one topology in the domain from another while configuring a multicast routing table, use the topology-id command in Intermediate System-to-Intermediate System (IS-IS) address family configuration submode. To disable the topology use the no form of the command.

topology-idisis-multicast-topology-id-number

notopology-idisis-multicast-topology-id-number

Syntax Description

isis-multicast-topology-id-number

ID number for a specific IS-IS multicast topology. Range is 6 to 4095.

Command Default

No topology is associated with a routing table by default.

Command Modes

IS-IS address family configuration

Command History

Release

Modification

Release 3.7.0

This command was introduced.

Usage Guidelines

Task ID

Task ID

Operations

isis

read, write

Examples

The following example shows how to differentiate a topology from another in the multicast routing table in IS-IS routing: